RAID HDDs spin up sequence

RAID HDDs spin up sequence

[Piergiorgio Sartor]

Hi all,

assuming there is a NAS, with, for example, 10 HDDs
in RAID-6. Assuming the HDDs are put in standby, in
order to save energy, when the NAS is not used.
How is the spin up sequence when the corresponding
/dev/mdX device is accessed?
Will the system spin up one HDD at time or all together?

Obviously, one at time will limit the peak current,
thus allowing a better dimensioned PSU, working almost
always around the optimal efficiency point.

Thanks a lot for any information on the topic,

bye,

-- 

piergiorgio

Re: RAID HDDs spin up sequence

[Roberto Spadim]

you psu must be dimensioned to work with everythink at full work load
(it´s a real production NAS right?! not a test)
your SAS/IDE/SATA controller and HDD manual should be checked
how hdd wake up? one command (read/write) over sata/sas/ide channel wake it up?
on linux raid we have a read algorithm and a write algorithm
if a raid1 write occur all disks will wake up
if a raid1 (raid0 or another) read occur only the disk will wake up

but check you SATA/IDE/SATA controller, how it wake up your disk, and
how you hdd wake up

2011/1/31 Piergiorgio Sartor <piergiorgio.sartor@nexgo.de>:
> Hi all,
>
> assuming there is a NAS, with, for example, 10 HDDs
> in RAID-6. Assuming the HDDs are put in standby, in
> order to save energy, when the NAS is not used.
> How is the spin up sequence when the corresponding
> /dev/mdX device is accessed?
> Will the system spin up one HDD at time or all together?
>
> Obviously, one at time will limit the peak current,
> thus allowing a better dimensioned PSU, working almost
> always around the optimal efficiency point.
>
> Thanks a lot for any information on the topic,
>
> bye,
>
> --
>
> piergiorgio
> --
> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>



-- 
Roberto Spadim
Spadim Technology / SPAEmpresarial
--
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Re: RAID HDDs spin up sequence

[Roberto Spadim]

normaly...
raid1 send many writes and one read
raid0 send one write and one read

2011/1/31 Roberto Spadim <roberto@spadim.com.br>:
> you psu must be dimensioned to work with everythink at full work load
> (it´s a real production NAS right?! not a test)
> your SAS/IDE/SATA controller and HDD manual should be checked
> how hdd wake up? one command (read/write) over sata/sas/ide channel wake it up?
> on linux raid we have a read algorithm and a write algorithm
> if a raid1 write occur all disks will wake up
> if a raid1 (raid0 or another) read occur only the disk will wake up
>
> but check you SATA/IDE/SATA controller, how it wake up your disk, and
> how you hdd wake up
>
> 2011/1/31 Piergiorgio Sartor <piergiorgio.sartor@nexgo.de>:
>> Hi all,
>>
>> assuming there is a NAS, with, for example, 10 HDDs
>> in RAID-6. Assuming the HDDs are put in standby, in
>> order to save energy, when the NAS is not used.
>> How is the spin up sequence when the corresponding
>> /dev/mdX device is accessed?
>> Will the system spin up one HDD at time or all together?
>>
>> Obviously, one at time will limit the peak current,
>> thus allowing a better dimensioned PSU, working almost
>> always around the optimal efficiency point.
>>
>> Thanks a lot for any information on the topic,
>>
>> bye,
>>
>> --
>>
>> piergiorgio
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>
>
>
>
> --
> Roberto Spadim
> Spadim Technology / SPAEmpresarial
>



-- 
Roberto Spadim
Spadim Technology / SPAEmpresarial
--
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Re: RAID HDDs spin up sequence

[Mathias Burén]

On 31 January 2011 21:09, Roberto Spadim <roberto@spadim.com.br> wrote:
> you psu must be dimensioned to work with everythink at full work load
> (it´s a real production NAS right?! not a test)
> your SAS/IDE/SATA controller and HDD manual should be checked
> how hdd wake up? one command (read/write) over sata/sas/ide channel wake it up?
> on linux raid we have a read algorithm and a write algorithm
> if a raid1 write occur all disks will wake up
> if a raid1 (raid0 or another) read occur only the disk will wake up
>
> but check you SATA/IDE/SATA controller, how it wake up your disk, and
> how you hdd wake up
>
> 2011/1/31 Piergiorgio Sartor <piergiorgio.sartor@nexgo.de>:
>> Hi all,
>>
>> assuming there is a NAS, with, for example, 10 HDDs
>> in RAID-6. Assuming the HDDs are put in standby, in
>> order to save energy, when the NAS is not used.
>> How is the spin up sequence when the corresponding
>> /dev/mdX device is accessed?
>> Will the system spin up one HDD at time or all together?
>>
>> Obviously, one at time will limit the peak current,
>> thus allowing a better dimensioned PSU, working almost
>> always around the optimal efficiency point.
>>
>> Thanks a lot for any information on the topic,
>>
>> bye,
>>
>> --
>>
>> piergiorgio
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>
>
>
>
> --
> Roberto Spadim
> Spadim Technology / SPAEmpresarial
> --
> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>

I would guess, that on a RAID0 setup, any read to that md device would
wake every disk up in that setup. No?

// Mathias
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Re: RAID HDDs spin up sequence

[Roberto Spadim]

just if you need information on all disks
define your read. are you reading 1 byte or many bytes (on all hds?)
the number of bytes read/write is the point
if you need another disk to read/write you need to wake up your another hd

check this implementations on mdadm:
linear, raid0, 0, stripe
maybe one is better for low power than another, but maybe one is
faster than another

2011/1/31 Mathias Burén <mathias.buren@gmail.com>:
> On 31 January 2011 21:09, Roberto Spadim <roberto@spadim.com.br> wrote:
>> you psu must be dimensioned to work with everythink at full work load
>> (it´s a real production NAS right?! not a test)
>> your SAS/IDE/SATA controller and HDD manual should be checked
>> how hdd wake up? one command (read/write) over sata/sas/ide channel wake it up?
>> on linux raid we have a read algorithm and a write algorithm
>> if a raid1 write occur all disks will wake up
>> if a raid1 (raid0 or another) read occur only the disk will wake up
>>
>> but check you SATA/IDE/SATA controller, how it wake up your disk, and
>> how you hdd wake up
>>
>> 2011/1/31 Piergiorgio Sartor <piergiorgio.sartor@nexgo.de>:
>>> Hi all,
>>>
>>> assuming there is a NAS, with, for example, 10 HDDs
>>> in RAID-6. Assuming the HDDs are put in standby, in
>>> order to save energy, when the NAS is not used.
>>> How is the spin up sequence when the corresponding
>>> /dev/mdX device is accessed?
>>> Will the system spin up one HDD at time or all together?
>>>
>>> Obviously, one at time will limit the peak current,
>>> thus allowing a better dimensioned PSU, working almost
>>> always around the optimal efficiency point.
>>>
>>> Thanks a lot for any information on the topic,
>>>
>>> bye,
>>>
>>> --
>>>
>>> piergiorgio
>>> --
>>> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
>>> the body of a message to majordomo@vger.kernel.org
>>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>>
>>
>>
>>
>> --
>> Roberto Spadim
>> Spadim Technology / SPAEmpresarial
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>
>
> I would guess, that on a RAID0 setup, any read to that md device would
> wake every disk up in that setup. No?
>
> // Mathias
>
>



-- 
Roberto Spadim
Spadim Technology / SPAEmpresarial
--
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Re: RAID HDDs spin up sequence

[Mathias Burén]

On 31 January 2011 21:25, Roberto Spadim <roberto@spadim.com.br> wrote:
> just if you need information on all disks
> define your read. are you reading 1 byte or many bytes (on all hds?)
> the number of bytes read/write is the point
> if you need another disk to read/write you need to wake up your another hd
>
> check this implementations on mdadm:
> linear, raid0, 0, stripe
> maybe one is better for low power than another, but maybe one is
> faster than another
>
> 2011/1/31 Mathias Burén <mathias.buren@gmail.com>:
>> On 31 January 2011 21:09, Roberto Spadim <roberto@spadim.com.br> wrote:
>>> you psu must be dimensioned to work with everythink at full work load
>>> (it´s a real production NAS right?! not a test)
>>> your SAS/IDE/SATA controller and HDD manual should be checked
>>> how hdd wake up? one command (read/write) over sata/sas/ide channel wake it up?
>>> on linux raid we have a read algorithm and a write algorithm
>>> if a raid1 write occur all disks will wake up
>>> if a raid1 (raid0 or another) read occur only the disk will wake up
>>>
>>> but check you SATA/IDE/SATA controller, how it wake up your disk, and
>>> how you hdd wake up
>>>
>>> 2011/1/31 Piergiorgio Sartor <piergiorgio.sartor@nexgo.de>:
>>>> Hi all,
>>>>
>>>> assuming there is a NAS, with, for example, 10 HDDs
>>>> in RAID-6. Assuming the HDDs are put in standby, in
>>>> order to save energy, when the NAS is not used.
>>>> How is the spin up sequence when the corresponding
>>>> /dev/mdX device is accessed?
>>>> Will the system spin up one HDD at time or all together?
>>>>
>>>> Obviously, one at time will limit the peak current,
>>>> thus allowing a better dimensioned PSU, working almost
>>>> always around the optimal efficiency point.
>>>>
>>>> Thanks a lot for any information on the topic,
>>>>
>>>> bye,
>>>>
>>>> --
>>>>
>>>> piergiorgio
>>>> --
>>>> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
>>>> the body of a message to majordomo@vger.kernel.org
>>>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>>>
>>>
>>>
>>>
>>> --
>>> Roberto Spadim
>>> Spadim Technology / SPAEmpresarial
>>> --
>>> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
>>> the body of a message to majordomo@vger.kernel.org
>>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>>
>>
>> I would guess, that on a RAID0 setup, any read to that md device would
>> wake every disk up in that setup. No?
>>
>> // Mathias
>>
>>
>
>
>
> --
> Roberto Spadim
> Spadim Technology / SPAEmpresarial
>

I meant "default RAID0 setup with mdadm", with a minimum of 2 HDDs,
and any fs on top of that. (with or without lvm)

Unless the file is very small (smaller than the minimum piece of data
that's being spread across all devices in the RAID0 setup (btw, that's
this called in RAID0, is it chunk size? Stripe size?)) or cached,
you'll wake the HDDs up. Right?

// Mathias
--
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Re: RAID HDDs spin up sequence

[Roberto Spadim]

i think yes (hd wake up on write/read command)
check linear and stripe layout
linear is like a lvm (concatenation)
i think raid0 work like stripe, but need to check it and return (raid0
= 0 = stripe level,  linear!=raid0 for linux implementation)

2011/1/31 Mathias Burén <mathias.buren@gmail.com>:
> On 31 January 2011 21:25, Roberto Spadim <roberto@spadim.com.br> wrote:
>> just if you need information on all disks
>> define your read. are you reading 1 byte or many bytes (on all hds?)
>> the number of bytes read/write is the point
>> if you need another disk to read/write you need to wake up your another hd
>>
>> check this implementations on mdadm:
>> linear, raid0, 0, stripe
>> maybe one is better for low power than another, but maybe one is
>> faster than another
>>
>> 2011/1/31 Mathias Burén <mathias.buren@gmail.com>:
>>> On 31 January 2011 21:09, Roberto Spadim <roberto@spadim.com.br> wrote:
>>>> you psu must be dimensioned to work with everythink at full work load
>>>> (it´s a real production NAS right?! not a test)
>>>> your SAS/IDE/SATA controller and HDD manual should be checked
>>>> how hdd wake up? one command (read/write) over sata/sas/ide channel wake it up?
>>>> on linux raid we have a read algorithm and a write algorithm
>>>> if a raid1 write occur all disks will wake up
>>>> if a raid1 (raid0 or another) read occur only the disk will wake up
>>>>
>>>> but check you SATA/IDE/SATA controller, how it wake up your disk, and
>>>> how you hdd wake up
>>>>
>>>> 2011/1/31 Piergiorgio Sartor <piergiorgio.sartor@nexgo.de>:
>>>>> Hi all,
>>>>>
>>>>> assuming there is a NAS, with, for example, 10 HDDs
>>>>> in RAID-6. Assuming the HDDs are put in standby, in
>>>>> order to save energy, when the NAS is not used.
>>>>> How is the spin up sequence when the corresponding
>>>>> /dev/mdX device is accessed?
>>>>> Will the system spin up one HDD at time or all together?
>>>>>
>>>>> Obviously, one at time will limit the peak current,
>>>>> thus allowing a better dimensioned PSU, working almost
>>>>> always around the optimal efficiency point.
>>>>>
>>>>> Thanks a lot for any information on the topic,
>>>>>
>>>>> bye,
>>>>>
>>>>> --
>>>>>
>>>>> piergiorgio
>>>>> --
>>>>> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
>>>>> the body of a message to majordomo@vger.kernel.org
>>>>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>>>>
>>>>
>>>>
>>>>
>>>> --
>>>> Roberto Spadim
>>>> Spadim Technology / SPAEmpresarial
>>>> --
>>>> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
>>>> the body of a message to majordomo@vger.kernel.org
>>>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>>>
>>>
>>> I would guess, that on a RAID0 setup, any read to that md device would
>>> wake every disk up in that setup. No?
>>>
>>> // Mathias
>>>
>>>
>>
>>
>>
>> --
>> Roberto Spadim
>> Spadim Technology / SPAEmpresarial
>>
>
> I meant "default RAID0 setup with mdadm", with a minimum of 2 HDDs,
> and any fs on top of that. (with or without lvm)
>
> Unless the file is very small (smaller than the minimum piece of data
> that's being spread across all devices in the RAID0 setup (btw, that's
> this called in RAID0, is it chunk size? Stripe size?)) or cached,
> you'll wake the HDDs up. Right?
>
> // Mathias
> --
> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>



-- 
Roberto Spadim
Spadim Technology / SPAEmpresarial
--
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Re: RAID HDDs spin up sequence

[Piergiorgio Sartor]

On Mon, Jan 31, 2011 at 07:09:24PM -0200, Roberto Spadim wrote:
> you psu must be dimensioned to work with everythink at full work load
> (it´s a real production NAS right?! not a test)
> your SAS/IDE/SATA controller and HDD manual should be checked
> how hdd wake up? one command (read/write) over sata/sas/ide channel wake it up?
> on linux raid we have a read algorithm and a write algorithm
> if a raid1 write occur all disks will wake up
> if a raid1 (raid0 or another) read occur only the disk will wake up
> 
> but check you SATA/IDE/SATA controller, how it wake up your disk, and
> how you hdd wake up

Hi, thanks for the answer, unfortunately I was
hoping to have made myself clear enough.

First of all, it is a RAID-6, so let's say that's
already decided by requirements. With SATA HDDs.

Second, the question was exactly about how the HDDs
are waked up. This is a SW issue, trying with normal
setups, i.e. a couple of disks, it is possible to
send them to sleep (hdparm -y /dev/hdX) and the wake
them up by a simple access.
I had no opportunity to check this with a RAID-5/6,
so I was asking if anyone knows.

Finally, in order to be power efficient, the PSU,
assuming something like an 80 Plus Gold, should work
at not less than 20% of the nominal power, otherwise
(according to some reviews), the efficiency drops far
below the 80%~90% declared by the 80 Plus standard
(which is measured at 20%, 50% and 100% of the maximum
specified power).
It seem it gets easily around 40%~50%.
So, the PSU must be somehow under dimensioned for the
spin up of 10 HDDs, which seem to require a possible
30W*10=300W (some nasty HDDs seem to require 30W, in
this situation) only for the storage.

If the HDDs spin up one after the other, then the peak
consumption is only 30W, which might allow a lower
power PSU, in contrast with the requirement to provide
300W alone for the spin up.

So, back to the original question, if a 10 HDDs RAID-6
is in standby, how do the single HDD will be waked up,
in case of access? Of course, a quite larger access,
i.e. some GiB of data.

Thanks again,

bye,

-- 

piergiorgio
--
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Re: RAID HDDs spin up sequence

[Roberto Spadim]

the better probability here is: all disks must be waked up
since you can have acces of 1gb but starting at a position that all
disks must be used
don´t try used small PSU
HP Proliant ML310G5 start all hardware on power up (a lot o Watts) and
after slow down thinks... why? check if PSU is ok, if not, don´t start
server. that´s a good PSU system.
ok if you want to test, i think the worst scenario is all disks beeing
waked up, i think linux use async (many threads) commands to send
write/read, maybe you will have a small time between wake up (maybe
just some microseconds)

2011/1/31 Piergiorgio Sartor <piergiorgio.sartor@nexgo.de>:
> On Mon, Jan 31, 2011 at 07:09:24PM -0200, Roberto Spadim wrote:
>> you psu must be dimensioned to work with everythink at full work load
>> (it愀 a real production NAS right?! not a test)
>> your SAS/IDE/SATA controller and HDD manual should be checked
>> how hdd wake up? one command (read/write) over sata/sas/ide channel wake it up?
>> on linux raid we have a read algorithm and a write algorithm
>> if a raid1 write occur all disks will wake up
>> if a raid1 (raid0 or another) read occur only the disk will wake up
>>
>> but check you SATA/IDE/SATA controller, how it wake up your disk, and
>> how you hdd wake up
>
> Hi, thanks for the answer, unfortunately I was
> hoping to have made myself clear enough.
>
> First of all, it is a RAID-6, so let's say that's
> already decided by requirements. With SATA HDDs.
>
> Second, the question was exactly about how the HDDs
> are waked up. This is a SW issue, trying with normal
> setups, i.e. a couple of disks, it is possible to
> send them to sleep (hdparm -y /dev/hdX) and the wake
> them up by a simple access.
> I had no opportunity to check this with a RAID-5/6,
> so I was asking if anyone knows.
>
> Finally, in order to be power efficient, the PSU,
> assuming something like an 80 Plus Gold, should work
> at not less than 20% of the nominal power, otherwise
> (according to some reviews), the efficiency drops far
> below the 80%~90% declared by the 80 Plus standard
> (which is measured at 20%, 50% and 100% of the maximum
> specified power).
> It seem it gets easily around 40%~50%.
> So, the PSU must be somehow under dimensioned for the
> spin up of 10 HDDs, which seem to require a possible
> 30W*10=300W (some nasty HDDs seem to require 30W, in
> this situation) only for the storage.
>
> If the HDDs spin up one after the other, then the peak
> consumption is only 30W, which might allow a lower
> power PSU, in contrast with the requirement to provide
> 300W alone for the spin up.
>
> So, back to the original question, if a 10 HDDs RAID-6
> is in standby, how do the single HDD will be waked up,
> in case of access? Of course, a quite larger access,
> i.e. some GiB of data.
>
> Thanks again,
>
> bye,
>
> --
>
> piergiorgio
> --
> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>



-- 
Roberto Spadim
Spadim Technology / SPAEmpresarial
--
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the body of a message to majordomo@vger.kernel.org
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Re: RAID HDDs spin up sequence

[Roberto Spadim]

source code is the best source of information
try here too (WIKI)
https://raid.wiki.kernel.org/index.php/Main_Page

2011/1/31 Roberto Spadim <roberto@spadim.com.br>:
> the better probability here is: all disks must be waked up
> since you can have acces of 1gb but starting at a position that all
> disks must be used
> don´t try used small PSU
> HP Proliant ML310G5 start all hardware on power up (a lot o Watts) and
> after slow down thinks... why? check if PSU is ok, if not, don´t start
> server. that´s a good PSU system.
> ok if you want to test, i think the worst scenario is all disks beeing
> waked up, i think linux use async (many threads) commands to send
> write/read, maybe you will have a small time between wake up (maybe
> just some microseconds)
>
> 2011/1/31 Piergiorgio Sartor <piergiorgio.sartor@nexgo.de>:
>> On Mon, Jan 31, 2011 at 07:09:24PM -0200, Roberto Spadim wrote:
>>> you psu must be dimensioned to work with everythink at full work load
>>> (it愀 a real production NAS right?! not a test)
>>> your SAS/IDE/SATA controller and HDD manual should be checked
>>> how hdd wake up? one command (read/write) over sata/sas/ide channel wake it up?
>>> on linux raid we have a read algorithm and a write algorithm
>>> if a raid1 write occur all disks will wake up
>>> if a raid1 (raid0 or another) read occur only the disk will wake up
>>>
>>> but check you SATA/IDE/SATA controller, how it wake up your disk, and
>>> how you hdd wake up
>>
>> Hi, thanks for the answer, unfortunately I was
>> hoping to have made myself clear enough.
>>
>> First of all, it is a RAID-6, so let's say that's
>> already decided by requirements. With SATA HDDs.
>>
>> Second, the question was exactly about how the HDDs
>> are waked up. This is a SW issue, trying with normal
>> setups, i.e. a couple of disks, it is possible to
>> send them to sleep (hdparm -y /dev/hdX) and the wake
>> them up by a simple access.
>> I had no opportunity to check this with a RAID-5/6,
>> so I was asking if anyone knows.
>>
>> Finally, in order to be power efficient, the PSU,
>> assuming something like an 80 Plus Gold, should work
>> at not less than 20% of the nominal power, otherwise
>> (according to some reviews), the efficiency drops far
>> below the 80%~90% declared by the 80 Plus standard
>> (which is measured at 20%, 50% and 100% of the maximum
>> specified power).
>> It seem it gets easily around 40%~50%.
>> So, the PSU must be somehow under dimensioned for the
>> spin up of 10 HDDs, which seem to require a possible
>> 30W*10=300W (some nasty HDDs seem to require 30W, in
>> this situation) only for the storage.
>>
>> If the HDDs spin up one after the other, then the peak
>> consumption is only 30W, which might allow a lower
>> power PSU, in contrast with the requirement to provide
>> 300W alone for the spin up.
>>
>> So, back to the original question, if a 10 HDDs RAID-6
>> is in standby, how do the single HDD will be waked up,
>> in case of access? Of course, a quite larger access,
>> i.e. some GiB of data.
>>
>> Thanks again,
>>
>> bye,
>>
>> --
>>
>> piergiorgio
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>
>
>
>
> --
> Roberto Spadim
> Spadim Technology / SPAEmpresarial
>



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Re: RAID HDDs spin up sequence

[Piergiorgio Sartor]

On Mon, Jan 31, 2011 at 08:42:25PM -0200, Roberto Spadim wrote:
> the better probability here is: all disks must be waked up
> since you can have acces of 1gb but starting at a position that all
> disks must be used
> don´t try used small PSU

No, that's not an option, HDDs must have staggered
spin up, which is, to certain extent, supported by
some SATA HDD manufactures (not all, it seems).

> HP Proliant ML310G5 start all hardware on power up (a lot o Watts) and
> after slow down thinks... why? check if PSU is ok, if not, don´t start
> server. that´s a good PSU system.

As I wrote, efficiency is paramount here.

> ok if you want to test, i think the worst scenario is all disks beeing
> waked up, i think linux use async (many threads) commands to send
> write/read, maybe you will have a small time between wake up (maybe
> just some microseconds)

That's interesting information. I suspected something
like async access could have happened.
Is this confirmed? Are the requests from md to the
device layer asynchronous?
How about libata? Does this serialize wake ups?

Thanks,

bye,

pg

> 2011/1/31 Piergiorgio Sartor <piergiorgio.sartor@nexgo.de>:
> > On Mon, Jan 31, 2011 at 07:09:24PM -0200, Roberto Spadim wrote:
> >> you psu must be dimensioned to work with everythink at full work load
> >> (it愀 a real production NAS right?! not a test)
> >> your SAS/IDE/SATA controller and HDD manual should be checked
> >> how hdd wake up? one command (read/write) over sata/sas/ide channel wake it up?
> >> on linux raid we have a read algorithm and a write algorithm
> >> if a raid1 write occur all disks will wake up
> >> if a raid1 (raid0 or another) read occur only the disk will wake up
> >>
> >> but check you SATA/IDE/SATA controller, how it wake up your disk, and
> >> how you hdd wake up
> >
> > Hi, thanks for the answer, unfortunately I was
> > hoping to have made myself clear enough.
> >
> > First of all, it is a RAID-6, so let's say that's
> > already decided by requirements. With SATA HDDs.
> >
> > Second, the question was exactly about how the HDDs
> > are waked up. This is a SW issue, trying with normal
> > setups, i.e. a couple of disks, it is possible to
> > send them to sleep (hdparm -y /dev/hdX) and the wake
> > them up by a simple access.
> > I had no opportunity to check this with a RAID-5/6,
> > so I was asking if anyone knows.
> >
> > Finally, in order to be power efficient, the PSU,
> > assuming something like an 80 Plus Gold, should work
> > at not less than 20% of the nominal power, otherwise
> > (according to some reviews), the efficiency drops far
> > below the 80%~90% declared by the 80 Plus standard
> > (which is measured at 20%, 50% and 100% of the maximum
> > specified power).
> > It seem it gets easily around 40%~50%.
> > So, the PSU must be somehow under dimensioned for the
> > spin up of 10 HDDs, which seem to require a possible
> > 30W*10=300W (some nasty HDDs seem to require 30W, in
> > this situation) only for the storage.
> >
> > If the HDDs spin up one after the other, then the peak
> > consumption is only 30W, which might allow a lower
> > power PSU, in contrast with the requirement to provide
> > 300W alone for the spin up.
> >
> > So, back to the original question, if a 10 HDDs RAID-6
> > is in standby, how do the single HDD will be waked up,
> > in case of access? Of course, a quite larger access,
> > i.e. some GiB of data.
> >
> > Thanks again,
> >
> > bye,
> >
> > --
> >
> > piergiorgio
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-raid" in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> >
> 
> 
> 
> -- 
> Roberto Spadim
> Spadim Technology / SPAEmpresarial

-- 

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Re: RAID HDDs spin up sequence

[Roberto Spadim]

you have scheduler (elevator) maybe checking this code is nice, but
it´s device based (linux)
check /sys/block/xxxx/
to make some tweaks
i don´t know the real implementation (must check source code) but i
think mdadm is over linux device layer (it don´t controll access to
disk), i think it´s async, and linux kernel make thinks more sync...
check you raid level source code
somethink like: raid6.c
it´s small
i think it´s async
does you know where linux kernel can get information (inside /sys or
/proc filesystem) to know if you disk is weak?
maybe a check and wait before send read command can be implemented...

2011/1/31 Piergiorgio Sartor <piergiorgio.sartor@nexgo.de>:
> On Mon, Jan 31, 2011 at 08:42:25PM -0200, Roberto Spadim wrote:
>> the better probability here is: all disks must be waked up
>> since you can have acces of 1gb but starting at a position that all
>> disks must be used
>> don´t try used small PSU
>
> No, that's not an option, HDDs must have staggered
> spin up, which is, to certain extent, supported by
> some SATA HDD manufactures (not all, it seems).
>
>> HP Proliant ML310G5 start all hardware on power up (a lot o Watts) and
>> after slow down thinks... why? check if PSU is ok, if not, don´t start
>> server. that´s a good PSU system.
>
> As I wrote, efficiency is paramount here.
>
>> ok if you want to test, i think the worst scenario is all disks beeing
>> waked up, i think linux use async (many threads) commands to send
>> write/read, maybe you will have a small time between wake up (maybe
>> just some microseconds)
>
> That's interesting information. I suspected something
> like async access could have happened.
> Is this confirmed? Are the requests from md to the
> device layer asynchronous?
> How about libata? Does this serialize wake ups?
>
> Thanks,
>
> bye,
>
> pg
>
>> 2011/1/31 Piergiorgio Sartor <piergiorgio.sartor@nexgo.de>:
>> > On Mon, Jan 31, 2011 at 07:09:24PM -0200, Roberto Spadim wrote:
>> >> you psu must be dimensioned to work with everythink at full work load
>> >> (it愀 a real production NAS right?! not a test)
>> >> your SAS/IDE/SATA controller and HDD manual should be checked
>> >> how hdd wake up? one command (read/write) over sata/sas/ide channel wake it up?
>> >> on linux raid we have a read algorithm and a write algorithm
>> >> if a raid1 write occur all disks will wake up
>> >> if a raid1 (raid0 or another) read occur only the disk will wake up
>> >>
>> >> but check you SATA/IDE/SATA controller, how it wake up your disk, and
>> >> how you hdd wake up
>> >
>> > Hi, thanks for the answer, unfortunately I was
>> > hoping to have made myself clear enough.
>> >
>> > First of all, it is a RAID-6, so let's say that's
>> > already decided by requirements. With SATA HDDs.
>> >
>> > Second, the question was exactly about how the HDDs
>> > are waked up. This is a SW issue, trying with normal
>> > setups, i.e. a couple of disks, it is possible to
>> > send them to sleep (hdparm -y /dev/hdX) and the wake
>> > them up by a simple access.
>> > I had no opportunity to check this with a RAID-5/6,
>> > so I was asking if anyone knows.
>> >
>> > Finally, in order to be power efficient, the PSU,
>> > assuming something like an 80 Plus Gold, should work
>> > at not less than 20% of the nominal power, otherwise
>> > (according to some reviews), the efficiency drops far
>> > below the 80%~90% declared by the 80 Plus standard
>> > (which is measured at 20%, 50% and 100% of the maximum
>> > specified power).
>> > It seem it gets easily around 40%~50%.
>> > So, the PSU must be somehow under dimensioned for the
>> > spin up of 10 HDDs, which seem to require a possible
>> > 30W*10=300W (some nasty HDDs seem to require 30W, in
>> > this situation) only for the storage.
>> >
>> > If the HDDs spin up one after the other, then the peak
>> > consumption is only 30W, which might allow a lower
>> > power PSU, in contrast with the requirement to provide
>> > 300W alone for the spin up.
>> >
>> > So, back to the original question, if a 10 HDDs RAID-6
>> > is in standby, how do the single HDD will be waked up,
>> > in case of access? Of course, a quite larger access,
>> > i.e. some GiB of data.
>> >
>> > Thanks again,
>> >
>> > bye,
>> >
>> > --
>> >
>> > piergiorgio
>> > --
>> > To unsubscribe from this list: send the line "unsubscribe linux-raid" in
>> > the body of a message to majordomo@vger.kernel.org
>> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
>> >
>>
>>
>>
>> --
>> Roberto Spadim
>> Spadim Technology / SPAEmpresarial
>
> --
>
> piergiorgio
> --
> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>



-- 
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Spadim Technology / SPAEmpresarial
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Re: RAID HDDs spin up sequence

[Phillip Susi]

On 01/31/2011 06:07 PM, Piergiorgio Sartor wrote:
> That's interesting information. I suspected something
> like async access could have happened.
> Is this confirmed? Are the requests from md to the
> device layer asynchronous?

Yes, it sends down requests to all drives simultaneously to achieve 
maximum performance.  This is the main purpose of raid-5.

> How about libata? Does this serialize wake ups?

It doesn't.  It will wake them all up at once.

If you want to force serial wakeup, you would need to do some hacking in 
libata or the scsi layer to only allow one wakeup request at once.  Of 
course, with a 6 disk raid where each disk takes 6 seconds to spin up, 
you will be waiting 36 seconds to get your data.  Not exactly desirable.

Re: RAID HDDs spin up sequence

[Roman Mamedov]

[-- Attachment #1: Type: text/plain, Size: 715 bytes --]

On Mon, 31 Jan 2011 20:45:22 -0500
Phillip Susi <psusi@cfl.rr.com> wrote:

> If you want to force serial wakeup, you would need to do some hacking in 
> libata or the scsi layer to only allow one wakeup request at once.  Of 
> course, with a 6 disk raid where each disk takes 6 seconds to spin up, 
> you will be waiting 36 seconds to get your data.  Not exactly desirable.

Well, if the other option is to have your system hard-reset because the PSU
overloads from 12-20-24 disks spinning up at once (you know staggered spin-up
is supported by disks/controllers for a reason), then the wait does not look so
bad.

My take on the problem: just don't spin down your RAIDs.

-- 
With respect,
Roman

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 198 bytes --]

Re: RAID HDDs spin up sequence

[John Robinson]

On 01/02/2011 01:45, Phillip Susi wrote:
> On 01/31/2011 06:07 PM, Piergiorgio Sartor wrote:
>> That's interesting information. I suspected something
>> like async access could have happened.
>> Is this confirmed? Are the requests from md to the
>> device layer asynchronous?
>
> Yes, it sends down requests to all drives simultaneously to achieve
> maximum performance. This is the main purpose of raid-5.
>
>> How about libata? Does this serialize wake ups?
>
> It doesn't. It will wake them all up at once.
>
> If you want to force serial wakeup, you would need to do some hacking in
> libata or the scsi layer to only allow one wakeup request at once. Of
> course, with a 6 disk raid where each disk takes 6 seconds to spin up,
> you will be waiting 36 seconds to get your data. Not exactly desirable.

That'd be an excessive amount of time to wait. A quarter of a second is 
more than enough, a tenth of a second would probably be enough. It's 
just the motor inrush current you're trying to avoid having simultaneously.

So waiting another second for your array to wake up would mean you could 
use a sensibly-sized PSU operating in its 80%+ efficiency range, rather 
than a huge PSU operating inefficiently.

Cheers,

John.

RE: RAID HDDs spin up sequence

[brian.foster]

> -----Original Message-----
> From: linux-raid-owner@vger.kernel.org [mailto:linux-raid-
> owner@vger.kernel.org] On Behalf Of Piergiorgio Sartor
> Sent: Monday, January 31, 2011 5:24 PM
> To: Roberto Spadim
> Cc: Piergiorgio Sartor; linux-raid@vger.kernel.org
> Subject: Re: RAID HDDs spin up sequence
> 
> On Mon, Jan 31, 2011 at 07:09:24PM -0200, Roberto Spadim wrote:
> > you psu must be dimensioned to work with everythink at full work load
> > (it´s a real production NAS right?! not a test)
> > your SAS/IDE/SATA controller and HDD manual should be checked
> > how hdd wake up? one command (read/write) over sata/sas/ide channel
> wake it up?
> > on linux raid we have a read algorithm and a write algorithm
> > if a raid1 write occur all disks will wake up
> > if a raid1 (raid0 or another) read occur only the disk will wake up
> >
> > but check you SATA/IDE/SATA controller, how it wake up your disk, and
> > how you hdd wake up
> 
> Hi, thanks for the answer, unfortunately I was
> hoping to have made myself clear enough.
> 
> First of all, it is a RAID-6, so let's say that's
> already decided by requirements. With SATA HDDs.
> 
> Second, the question was exactly about how the HDDs
> are waked up. This is a SW issue, trying with normal
> setups, i.e. a couple of disks, it is possible to
> send them to sleep (hdparm -y /dev/hdX) and the wake
> them up by a simple access.
> I had no opportunity to check this with a RAID-5/6,
> so I was asking if anyone knows.
> 
> Finally, in order to be power efficient, the PSU,
> assuming something like an 80 Plus Gold, should work
> at not less than 20% of the nominal power, otherwise
> (according to some reviews), the efficiency drops far
> below the 80%~90% declared by the 80 Plus standard
> (which is measured at 20%, 50% and 100% of the maximum
> specified power).
> It seem it gets easily around 40%~50%.
> So, the PSU must be somehow under dimensioned for the
> spin up of 10 HDDs, which seem to require a possible
> 30W*10=300W (some nasty HDDs seem to require 30W, in
> this situation) only for the storage.
> 
> If the HDDs spin up one after the other, then the peak
> consumption is only 30W, which might allow a lower
> power PSU, in contrast with the requirement to provide
> 300W alone for the spin up.
> 
> So, back to the original question, if a 10 HDDs RAID-6
> is in standby, how do the single HDD will be waked up,
> in case of access? Of course, a quite larger access,
> i.e. some GiB of data.

We have a similar situation with our Iomega NAS products. We had a fairly crude locking mechanism implemented at the SCSI level that suits our needs to support staggered spin up. As indicated previously, we find that a 1 or 2 second delay between spin ups modulates the current draw enough such that we don't run into problems. We use this in conjunction with MD without much of a problem.

I'm not sure that the code as implemented is appropriate for mainline inclusion (and I'm not going to post it directly), but FYI the patches are included in the open source tarball that is made available on the support section of the iomega.com website (hint: check out the ix12 support & downloads section).

Brian

> 
> Thanks again,
> 
> bye,
> 
> --
> 
> piergiorgio
> --
> To unsubscribe from this list: send the line "unsubscribe linux-raid"
> in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

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Re: RAID HDDs spin up sequence

[Roberto Spadim]

maybe a check inside mdadm code should be implemented

before send read/write command check if device is sleeping,
if yes
if previous devices wakeup command was more than x seconds OR no
device, send a wakeup command

another idea: a fixed delay to wake up, diferent per device, but could
only work when we send(before sleep part of code) to all devices
command at the same time

mdadm should be changed (options be included) and kernel source too

2011/2/1  <brian.foster@emc.com>:
>> -----Original Message-----
>> From: linux-raid-owner@vger.kernel.org [mailto:linux-raid-
>> owner@vger.kernel.org] On Behalf Of Piergiorgio Sartor
>> Sent: Monday, January 31, 2011 5:24 PM
>> To: Roberto Spadim
>> Cc: Piergiorgio Sartor; linux-raid@vger.kernel.org
>> Subject: Re: RAID HDDs spin up sequence
>>
>> On Mon, Jan 31, 2011 at 07:09:24PM -0200, Roberto Spadim wrote:
>> > you psu must be dimensioned to work with everythink at full work load
>> > (it愀 a real production NAS right?! not a test)
>> > your SAS/IDE/SATA controller and HDD manual should be checked
>> > how hdd wake up? one command (read/write) over sata/sas/ide channel
>> wake it up?
>> > on linux raid we have a read algorithm and a write algorithm
>> > if a raid1 write occur all disks will wake up
>> > if a raid1 (raid0 or another) read occur only the disk will wake up
>> >
>> > but check you SATA/IDE/SATA controller, how it wake up your disk, and
>> > how you hdd wake up
>>
>> Hi, thanks for the answer, unfortunately I was
>> hoping to have made myself clear enough.
>>
>> First of all, it is a RAID-6, so let's say that's
>> already decided by requirements. With SATA HDDs.
>>
>> Second, the question was exactly about how the HDDs
>> are waked up. This is a SW issue, trying with normal
>> setups, i.e. a couple of disks, it is possible to
>> send them to sleep (hdparm -y /dev/hdX) and the wake
>> them up by a simple access.
>> I had no opportunity to check this with a RAID-5/6,
>> so I was asking if anyone knows.
>>
>> Finally, in order to be power efficient, the PSU,
>> assuming something like an 80 Plus Gold, should work
>> at not less than 20% of the nominal power, otherwise
>> (according to some reviews), the efficiency drops far
>> below the 80%~90% declared by the 80 Plus standard
>> (which is measured at 20%, 50% and 100% of the maximum
>> specified power).
>> It seem it gets easily around 40%~50%.
>> So, the PSU must be somehow under dimensioned for the
>> spin up of 10 HDDs, which seem to require a possible
>> 30W*10=300W (some nasty HDDs seem to require 30W, in
>> this situation) only for the storage.
>>
>> If the HDDs spin up one after the other, then the peak
>> consumption is only 30W, which might allow a lower
>> power PSU, in contrast with the requirement to provide
>> 300W alone for the spin up.
>>
>> So, back to the original question, if a 10 HDDs RAID-6
>> is in standby, how do the single HDD will be waked up,
>> in case of access? Of course, a quite larger access,
>> i.e. some GiB of data.
>
> We have a similar situation with our Iomega NAS products. We had a fairly crude locking mechanism implemented at the SCSI level that suits our needs to support staggered spin up. As indicated previously, we find that a 1 or 2 second delay between spin ups modulates the current draw enough such that we don't run into problems. We use this in conjunction with MD without much of a problem.
>
> I'm not sure that the code as implemented is appropriate for mainline inclusion (and I'm not going to post it directly), but FYI the patches are included in the open source tarball that is made available on the support section of the iomega.com website (hint: check out the ix12 support & downloads section).
>
> Brian
>
>>
>> Thanks again,
>>
>> bye,
>>
>> --
>>
>> piergiorgio
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-raid"
>> in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>



-- 
Roberto Spadim
Spadim Technology / SPAEmpresarial
--
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Re: RAID HDDs spin up sequence

[Roberto Spadim]

try to put big capacitors and inductors on energy cable... it´s a good
eletric level solution... capacitor and inductors will help the start
current/voltage oscilation

2011/2/1 Roberto Spadim <roberto@spadim.com.br>:
> maybe a check inside mdadm code should be implemented
>
> before send read/write command check if device is sleeping,
> if yes
> if previous devices wakeup command was more than x seconds OR no
> device, send a wakeup command
>
> another idea: a fixed delay to wake up, diferent per device, but could
> only work when we send(before sleep part of code) to all devices
> command at the same time
>
> mdadm should be changed (options be included) and kernel source too
>
> 2011/2/1  <brian.foster@emc.com>:
>>> -----Original Message-----
>>> From: linux-raid-owner@vger.kernel.org [mailto:linux-raid-
>>> owner@vger.kernel.org] On Behalf Of Piergiorgio Sartor
>>> Sent: Monday, January 31, 2011 5:24 PM
>>> To: Roberto Spadim
>>> Cc: Piergiorgio Sartor; linux-raid@vger.kernel.org
>>> Subject: Re: RAID HDDs spin up sequence
>>>
>>> On Mon, Jan 31, 2011 at 07:09:24PM -0200, Roberto Spadim wrote:
>>> > you psu must be dimensioned to work with everythink at full work load
>>> > (it愀 a real production NAS right?! not a test)
>>> > your SAS/IDE/SATA controller and HDD manual should be checked
>>> > how hdd wake up? one command (read/write) over sata/sas/ide channel
>>> wake it up?
>>> > on linux raid we have a read algorithm and a write algorithm
>>> > if a raid1 write occur all disks will wake up
>>> > if a raid1 (raid0 or another) read occur only the disk will wake up
>>> >
>>> > but check you SATA/IDE/SATA controller, how it wake up your disk, and
>>> > how you hdd wake up
>>>
>>> Hi, thanks for the answer, unfortunately I was
>>> hoping to have made myself clear enough.
>>>
>>> First of all, it is a RAID-6, so let's say that's
>>> already decided by requirements. With SATA HDDs.
>>>
>>> Second, the question was exactly about how the HDDs
>>> are waked up. This is a SW issue, trying with normal
>>> setups, i.e. a couple of disks, it is possible to
>>> send them to sleep (hdparm -y /dev/hdX) and the wake
>>> them up by a simple access.
>>> I had no opportunity to check this with a RAID-5/6,
>>> so I was asking if anyone knows.
>>>
>>> Finally, in order to be power efficient, the PSU,
>>> assuming something like an 80 Plus Gold, should work
>>> at not less than 20% of the nominal power, otherwise
>>> (according to some reviews), the efficiency drops far
>>> below the 80%~90% declared by the 80 Plus standard
>>> (which is measured at 20%, 50% and 100% of the maximum
>>> specified power).
>>> It seem it gets easily around 40%~50%.
>>> So, the PSU must be somehow under dimensioned for the
>>> spin up of 10 HDDs, which seem to require a possible
>>> 30W*10=300W (some nasty HDDs seem to require 30W, in
>>> this situation) only for the storage.
>>>
>>> If the HDDs spin up one after the other, then the peak
>>> consumption is only 30W, which might allow a lower
>>> power PSU, in contrast with the requirement to provide
>>> 300W alone for the spin up.
>>>
>>> So, back to the original question, if a 10 HDDs RAID-6
>>> is in standby, how do the single HDD will be waked up,
>>> in case of access? Of course, a quite larger access,
>>> i.e. some GiB of data.
>>
>> We have a similar situation with our Iomega NAS products. We had a fairly crude locking mechanism implemented at the SCSI level that suits our needs to support staggered spin up. As indicated previously, we find that a 1 or 2 second delay between spin ups modulates the current draw enough such that we don't run into problems. We use this in conjunction with MD without much of a problem.
>>
>> I'm not sure that the code as implemented is appropriate for mainline inclusion (and I'm not going to post it directly), but FYI the patches are included in the open source tarball that is made available on the support section of the iomega.com website (hint: check out the ix12 support & downloads section).
>>
>> Brian
>>
>>>
>>> Thanks again,
>>>
>>> bye,
>>>
>>> --
>>>
>>> piergiorgio
>>> --
>>> To unsubscribe from this list: send the line "unsubscribe linux-raid"
>>> in
>>> the body of a message to majordomo@vger.kernel.org
>>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>>
>
>
>
> --
> Roberto Spadim
> Spadim Technology / SPAEmpresarial
>



-- 
Roberto Spadim
Spadim Technology / SPAEmpresarial
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Re: RAID HDDs spin up sequence

[John Robinson]

On 01/02/2011 14:44, Roberto Spadim wrote:
> try to put big capacitors and inductors on energy cable... it´s a good
> eletric level solution... capacitor and inductors will help the start
> current/voltage oscilation

No, it isn't; they'd cause excessive power draw on initial power-up.

Cheers,

John.

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Re: RAID HDDs spin up sequence

[Roberto Spadim]

hum that´s right.
maybe a power-up safe eletronic could be implemented
i don´t know if implementation is faster out of linux (hardware) or
inside (code)
using code is easy to port it to any hardware
maybe neil have interest in implement it in source code (i don´t know
if there´s more linux (kernel) developer here in list)

2011/2/1 John Robinson <john.robinson@anonymous.org.uk>:
> On 01/02/2011 14:44, Roberto Spadim wrote:
>>
>> try to put big capacitors and inductors on energy cable... it´s a good
>> eletric level solution... capacitor and inductors will help the start
>> current/voltage oscilation
>
> No, it isn't; they'd cause excessive power draw on initial power-up.
>
> Cheers,
>
> John.
>
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-- 
Roberto Spadim
Spadim Technology / SPAEmpresarial
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Re: RAID HDDs spin up sequence

[Stan Hoeppner]

John Robinson put forth on 2/1/2011 7:10 AM:

> That'd be an excessive amount of time to wait. A quarter of a second is more
> than enough, a tenth of a second would probably be enough. It's just the motor
> inrush current you're trying to avoid having simultaneously.

The blowers in a typical 2U server chassis will have slightly more startup
current draw than the drives, assuming 5 80mm blowers and 8 2.5" drives.  Mobos
don't do staggered startup of blowers.  Thus, staggering the drive spin up is
pointless.  Add to that the fact that most server chassis ship with PSUs large
enough to carry the current draw of anything/everything you can stuff into them.

> So waiting another second for your array to wake up would mean you could use a
> sensibly-sized PSU operating in its 80%+ efficiency range, rather than a huge
> PSU operating inefficiently.

A typical 2.5" 10K RPM 600GB enterprise HDD, such as the Seagate Savvio, has a
startup draw of 24.1 watts combined from the 12v and 5v rails.  A RAID/JBOD
chassis of 24 such drives, which is sold by dozens of vendors today, will draw
only 578.4 watts with all drives spinning up concurrently.  Most such chassis on
the market today are sold with 800w to 1800w redundant PSUs, again, making
staggered spin up moot.

-- 
Stan

Re: RAID HDDs spin up sequence

[Roberto Spadim]

some hardware solutions....
change PSU
change hard disk to solid state disks (OCZ is fast, energy saver, with
high MTBF, a very good disk is OCZ VERTEX 2, REVODRIVE (pci-express)
and OCZ AGILITY 2, check read random 4kb >=200 MB/s is better than any
SAS disk... latency is <0.1ms)

maybe changing to solid state is a good solution (cost is the point here)
another point is when startup remove (hot plug) some disks, and plug after

2011/2/1 Stan Hoeppner <stan@hardwarefreak.com>:
> John Robinson put forth on 2/1/2011 7:10 AM:
>
>> That'd be an excessive amount of time to wait. A quarter of a second is more
>> than enough, a tenth of a second would probably be enough. It's just the motor
>> inrush current you're trying to avoid having simultaneously.
>
> The blowers in a typical 2U server chassis will have slightly more startup
> current draw than the drives, assuming 5 80mm blowers and 8 2.5" drives.  Mobos
> don't do staggered startup of blowers.  Thus, staggering the drive spin up is
> pointless.  Add to that the fact that most server chassis ship with PSUs large
> enough to carry the current draw of anything/everything you can stuff into them.
>
>> So waiting another second for your array to wake up would mean you could use a
>> sensibly-sized PSU operating in its 80%+ efficiency range, rather than a huge
>> PSU operating inefficiently.
>
> A typical 2.5" 10K RPM 600GB enterprise HDD, such as the Seagate Savvio, has a
> startup draw of 24.1 watts combined from the 12v and 5v rails.  A RAID/JBOD
> chassis of 24 such drives, which is sold by dozens of vendors today, will draw
> only 578.4 watts with all drives spinning up concurrently.  Most such chassis on
> the market today are sold with 800w to 1800w redundant PSUs, again, making
> staggered spin up moot.
>
> --
> Stan
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>



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Roberto Spadim
Spadim Technology / SPAEmpresarial
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