doubts about sdd raid1 and cfs

doubts about sdd raid1 and cfs

[Roberto Spadim]

hi guys, i`m setting up a new server, it have
1) 2x 256gb sdd
Samsung SSD 850 PRO 256GB, EXM02B6Q
500118192 sectors, multi 1: LBA48 NCQ (depth 31/32)
2)1tb hdd
Hitachi HUA722010CLA330, JP4OA3EA
1953525168 sectors, multi 16: LBA48 NCQ (depth 31/32)

i`m plannig a raid1 with ssd and hdd, hdd being a "write-mostly", and
750gb of hdd i will use to backup or other useless files

i have somedoubts about the setup..
i use xfs at filesystem, should i consider TRIM command at filesystem?
the problem is hdd being part of raid1 setup with others ssd, could
the ssd receive the TRIM and the hdd too?
any idea is wellcome

-- 
Roberto Spadim

Re: doubts about sdd raid1 and cfs

[Mikael Abrahamsson]

On Sat, 13 Jun 2015, Roberto Spadim wrote:

> hi guys, i`m setting up a new server, it have
> 1) 2x 256gb sdd
> Samsung SSD 850 PRO 256GB, EXM02B6Q
> 500118192 sectors, multi 1: LBA48 NCQ (depth 31/32)
> 2)1tb hdd
> Hitachi HUA722010CLA330, JP4OA3EA
> 1953525168 sectors, multi 16: LBA48 NCQ (depth 31/32)
>
> i`m plannig a raid1 with ssd and hdd, hdd being a "write-mostly", and
> 750gb of hdd i will use to backup or other useless files
>
> i have somedoubts about the setup..
> i use xfs at filesystem, should i consider TRIM command at filesystem?
> the problem is hdd being part of raid1 setup with others ssd, could
> the ssd receive the TRIM and the hdd too?
> any idea is wellcome

Frankly, reading about the firmware problems on Samsung SSDs in 
combination with TRIM, I would recommend against using TRIM on samsung 
drives.

https://bugs.launchpad.net/ubuntu/+source/fstrim/+bug/1449005

-- 
Mikael Abrahamsson    email: swmike@swm.pp.se

Re: doubts about sdd raid1 and cfs

[Roberto Spadim]

hum, but what about the 850 version instead of 840?

2015-06-13 17:14 GMT-03:00 Mikael Abrahamsson <swmike@swm.pp.se>:
> On Sat, 13 Jun 2015, Roberto Spadim wrote:
>
>> hi guys, i`m setting up a new server, it have
>> 1) 2x 256gb sdd
>> Samsung SSD 850 PRO 256GB, EXM02B6Q
>> 500118192 sectors, multi 1: LBA48 NCQ (depth 31/32)
>> 2)1tb hdd
>> Hitachi HUA722010CLA330, JP4OA3EA
>> 1953525168 sectors, multi 16: LBA48 NCQ (depth 31/32)
>>
>> i`m plannig a raid1 with ssd and hdd, hdd being a "write-mostly", and
>> 750gb of hdd i will use to backup or other useless files
>>
>> i have somedoubts about the setup..
>> i use xfs at filesystem, should i consider TRIM command at filesystem?
>> the problem is hdd being part of raid1 setup with others ssd, could
>> the ssd receive the TRIM and the hdd too?
>> any idea is wellcome
>
>
> Frankly, reading about the firmware problems on Samsung SSDs in combination
> with TRIM, I would recommend against using TRIM on samsung drives.
>
> https://bugs.launchpad.net/ubuntu/+source/fstrim/+bug/1449005
>
> --
> Mikael Abrahamsson    email: swmike@swm.pp.se



-- 
Roberto Spadim
SPAEmpresarial - Software ERP
Eng. Automação e Controle
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Re: doubts about sdd raid1 and cfs

[Mikael Abrahamsson]

On Sat, 13 Jun 2015, Roberto Spadim wrote:

> hum, but what about the 850 version instead of 840?

SSDs have been around for more than 5 years (intel released the X25-M 
in 2008 according to wikipedia), TRIM has been around for 4-5 years.

I have seen so many problems related to TRIM, that I will not use it 
unless it comes default on from a manufacturer that has tested the entire 
chain, including hardware and software (my Apple laptop for instance).

We have seen TRIM not being NCQ enabled and stalling performance when 
doing TRIM, we have seen firmware bugs that cause drives to lose data when 
doing TRIM, we have seen Linux kernel bugs that also caused loss of data.

First of all, ask yourself why you want TRIM, understand how it works and 
if you will benefit, do your research properly, and then enable it.

Personally, I overprovision my SSDs instead:

http://www.samsung.com/global/business/semiconductor/minisite/SSD/global/html/whitepaper/whitepaper05.html
https://en.wikipedia.org/wiki/Write_amplification#Over-provisioning
http://www.seagate.com/gb/en/tech-insights/ssd-over-provisioning-benefits-master-ti/
http://www.edn.com/design/systems-design/4404566/Understanding-SSD-over-provisioning
http://www.kingston.com/en/ssd/overprovisioning

So I basically leave space on the drive that I don't use. In your case I 
would only partition 200GB (or even less) of that 240GB drive, and I would 
run it without TRIM.

-- 
Mikael Abrahamsson    email: swmike@swm.pp.se

Re: doubts about sdd raid1 and cfs

[Roberto Spadim]

nice :)
about the space, that was my next doubt ehhe thanks ! leave 40gb to
ssd "bad blocks"

about the writemostly, any comment?

2015-06-13 17:32 GMT-03:00 Mikael Abrahamsson <swmike@swm.pp.se>:
> On Sat, 13 Jun 2015, Roberto Spadim wrote:
>
>> hum, but what about the 850 version instead of 840?
>
>
> SSDs have been around for more than 5 years (intel released the X25-M in
> 2008 according to wikipedia), TRIM has been around for 4-5 years.
>
> I have seen so many problems related to TRIM, that I will not use it unless
> it comes default on from a manufacturer that has tested the entire chain,
> including hardware and software (my Apple laptop for instance).
>
> We have seen TRIM not being NCQ enabled and stalling performance when doing
> TRIM, we have seen firmware bugs that cause drives to lose data when doing
> TRIM, we have seen Linux kernel bugs that also caused loss of data.
>
> First of all, ask yourself why you want TRIM, understand how it works and if
> you will benefit, do your research properly, and then enable it.
>
> Personally, I overprovision my SSDs instead:
>
> http://www.samsung.com/global/business/semiconductor/minisite/SSD/global/html/whitepaper/whitepaper05.html
> https://en.wikipedia.org/wiki/Write_amplification#Over-provisioning
> http://www.seagate.com/gb/en/tech-insights/ssd-over-provisioning-benefits-master-ti/
> http://www.edn.com/design/systems-design/4404566/Understanding-SSD-over-provisioning
> http://www.kingston.com/en/ssd/overprovisioning
>
> So I basically leave space on the drive that I don't use. In your case I
> would only partition 200GB (or even less) of that 240GB drive, and I would
> run it without TRIM.
>
>
> --
> Mikael Abrahamsson    email: swmike@swm.pp.se



-- 
Roberto Spadim
SPAEmpresarial - Software ERP
Eng. Automação e Controle
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