[QUESTION] Sata RAID

[QUESTION] Sata RAID

[Patrick Ale]

Hi,

Quick question,

Since I am going to open my server today to do some pata tests (for
the weird detection problems people are giving me fantastic help with,
no sarcasm, I really mean it) I thought: why not add two 320GB SATA
disks on the SATA controller that the mainboard has.

I am wondering: should I use the onboard RAID function? Is this
supported by Linux? I remember back in "the old days (TM)" there were
seperate (spelling) drivers for ataraid, how does the current 2.6
branch cope with the RAID functions of modern motherboards?

I am aware that it is NOT hardware raid, the raid is done in the
driver, which is why you need this fancy boot disk before installing
Windows on your RAID set.

Or would you suggest me to stick with MD devices?


Cheers,

Patrick Ale
patrick.ale@gmail.com

"kun kasvan isoksi, halun olla poro"

Re: [QUESTION] Sata RAID

[Bartlomiej Zolnierkiewicz]

use device mapper and dmraid

	http://people.redhat.com/~heinzm/sw/dmraid/

and please read

	http://linux-ata.org/faq-sata-raid.html

On Saturday 24 February 2007, Patrick Ale wrote:
> Hi,
> 
> Quick question,
> 
> Since I am going to open my server today to do some pata tests (for
> the weird detection problems people are giving me fantastic help with,
> no sarcasm, I really mean it) I thought: why not add two 320GB SATA
> disks on the SATA controller that the mainboard has.
> 
> I am wondering: should I use the onboard RAID function? Is this
> supported by Linux? I remember back in "the old days (TM)" there were
> seperate (spelling) drivers for ataraid, how does the current 2.6
> branch cope with the RAID functions of modern motherboards?
> 
> I am aware that it is NOT hardware raid, the raid is done in the
> driver, which is why you need this fancy boot disk before installing
> Windows on your RAID set.
> 
> Or would you suggest me to stick with MD devices?
> 
> 
> Cheers,
> 
> Patrick Ale
> patrick.ale@gmail.com
> 
> "kun kasvan isoksi, halun olla poro"

Re: [QUESTION] Sata RAID

[Michael-Luke Jones]

But using 'fakeraid' (i.e. BIOS RAID) together with dmraid is  
generally discouraged in favour of using the more stable and well  
supported Linux Software RAID functionality.

Michael-Luke

On 24 Feb 2007, at 15:24, Bartlomiej Zolnierkiewicz wrote:

>
> use device mapper and dmraid
>
> 	http://people.redhat.com/~heinzm/sw/dmraid/
>
> and please read
>
> 	http://linux-ata.org/faq-sata-raid.html
>
> On Saturday 24 February 2007, Patrick Ale wrote:
>> Hi,
>>
>> Quick question,
>>
>> Since I am going to open my server today to do some pata tests (for
>> the weird detection problems people are giving me fantastic help  
>> with,
>> no sarcasm, I really mean it) I thought: why not add two 320GB SATA
>> disks on the SATA controller that the mainboard has.
>>
>> I am wondering: should I use the onboard RAID function? Is this
>> supported by Linux? I remember back in "the old days (TM)" there were
>> seperate (spelling) drivers for ataraid, how does the current 2.6
>> branch cope with the RAID functions of modern motherboards?
>>
>> I am aware that it is NOT hardware raid, the raid is done in the
>> driver, which is why you need this fancy boot disk before installing
>> Windows on your RAID set.
>>
>> Or would you suggest me to stick with MD devices?
>>
>>
>> Cheers,
>>
>> Patrick Ale
>> patrick.ale@gmail.com
>>
>> "kun kasvan isoksi, halun olla poro"
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>

Re: [QUESTION] Sata RAID

[Patrick Ale]

On 2/24/07, Michael-Luke Jones <jonesml@fastmail.to> wrote:
> But using 'fakeraid' (i.e. BIOS RAID) together with dmraid is
> generally discouraged in favour of using the more stable and well
> supported Linux Software RAID functionality.
>
> Michael-Luke

I think I actually used dmraid, and the problem I had in those days
was that it was just a layer over your legacy IDE drivers.

With 2.4 you had "real" drivers whom created block devices if I recall
correctly which you could really treat as disks.

If dmraid still works as it did in the days I used it it's just a
layer, like LVM, and the kernel itself doesnt care at all for the
disks being in a RAID set or not and will access the disks
independently, this I really found a reason to not use dmraid and
stick with MD devices.

And by the reactions from you guys I guess those reasons still exist :)

So MD it is,

Thanks!

Patrick

Re: [QUESTION] Sata RAID

[Patrick Ale]

On 2/24/07, Patrick Ale <patrick.ale@gmail.com> wrote:
> On 2/24/07, Michael-Luke Jones <jonesml@fastmail.to> wrote:

One more question regarding this, I am aware its not *really* kernel
related but answering this question now will save yourself a lot of
bogus emails from me about MD oopses later and all, and I want to
setup my disks right once and for all and never witness what I
witnessed last weeks with my ATA disks.

Would you use MD at all, taking in account the disks come from the
same batch and all? I hear these things about MD/RAID being pointless
when you use disks from the same brand/type/batch since they most
likely will break shortly after eachother.

Oh, and one more thing

              \|/ ____ \|/
              "@'/ ,. \`@"
              /_| \__/ |_\
                 \__U_/
<--- whoeveer programmed that into the sparc-linux oops is GOD, you're
my true hero, lol.


Patrick

Re: [QUESTION] Sata RAID

[Neil Brown]

On Monday February 26, patrick.ale@gmail.com wrote:
> On 2/24/07, Patrick Ale <patrick.ale@gmail.com> wrote:
> > On 2/24/07, Michael-Luke Jones <jonesml@fastmail.to> wrote:
> 
> One more question regarding this, I am aware its not *really* kernel
> related but answering this question now will save yourself a lot of
> bogus emails from me about MD oopses later and all, and I want to
> setup my disks right once and for all and never witness what I
> witnessed last weeks with my ATA disks.
> 
> Would you use MD at all, taking in account the disks come from the
> same batch and all? I hear these things about MD/RAID being pointless
> when you use disks from the same brand/type/batch since they most
> likely will break shortly after eachother.

Well, it the drives break shortly after each other, you lose your data
no matter what is happening.

But if it is just occasional read errors, md/raid handles those quite
well these days, over-writing the bad block with correct data.

Of course write error cause the drive to be kicked from the array, but
a write error on a modern drive means something much worse that a bit
of bad media has happened.

If I wanted raid1/5/6 I would certainly use md no-matter what batch
the drives were from (but maybe I am a tiny bit biased).

NeilBrown

Re: [QUESTION] Sata RAID

[Bill Davidsen]

Patrick Ale wrote:
> On 2/24/07, Patrick Ale <patrick.ale@gmail.com> wrote:
>> On 2/24/07, Michael-Luke Jones <jonesml@fastmail.to> wrote:
> 
> One more question regarding this, I am aware its not *really* kernel
> related but answering this question now will save yourself a lot of
> bogus emails from me about MD oopses later and all, and I want to
> setup my disks right once and for all and never witness what I
> witnessed last weeks with my ATA disks.
> 
> Would you use MD at all, taking in account the disks come from the
> same batch and all? I hear these things about MD/RAID being pointless
> when you use disks from the same brand/type/batch since they most
> likely will break shortly after each other.

Well, for values of "shortly" in months in most cases. These are 
consumer goods, I would not expect units with consecutive serial numbers 
to fail separated by such a short time that you can't do a backup and/or 
replace and rebuild. If quality control were so good they are likely to 
fail at the same time it would be so good they would be obsolete before 
they failed.

That urban myth is a good reason to do backups, but a bad reason to 
avoid RAID.

-- 
Bill Davidsen <davidsen@tmr.com>
   "We have more to fear from the bungling of the incompetent than from
the machinations of the wicked."  - from Slashdot

Re: [QUESTION] Sata RAID

[Alan]

> > Would you use MD at all, taking in account the disks come from the
> > same batch and all? I hear these things about MD/RAID being pointless
> > when you use disks from the same brand/type/batch since they most
> > likely will break shortly after each other.
> 
> Well, for values of "shortly" in months in most cases. These are 
> consumer goods, I would not expect units with consecutive serial numbers 
> to fail separated by such a short time that you can't do a backup and/or 

I've had them fail within days when using almost identical serial
numbers. Nowdays I just mix disk vendors on each array. End of problem.