How-to for enabling TRIM for SSD RAID-1 arrays?

How-to for enabling TRIM for SSD RAID-1 arrays?

[Derek Piper]

Hi,

Having found a posting on this list from July this year, I am trying to
find if (and how) TRIM support is supported and enabled under RAID 1 with 2
SSD drives.

The posting was mentioned that it was included in the kernel source as of
October 11th 2012.

I see nothing on the RAID wiki for enabling TRIM for SSD backed arrays. Any
pointers?

I have a system with Debian 7 (Kernel 3.2, mdadm 3.2.5) that I am working
on.

Thanks in advance,

Derek

-- 
Derek Piper - derek.piper@gmail.com

Re: How-to for enabling TRIM for SSD RAID-1 arrays?

[Roberto Spadim]

trim is enabled at mount option of filesystem (mount -t ext4 /dev/md0
/home -o discard)
for ext4 it's discard option if i'm not wrong
last kernels have trim support in software raid-1 (md raid1 driver),
just mount the filesystem over it and use, i don't know the exact
kernel version but it's ~1 year old feature

2013/9/13 Derek Piper <derek.piper@gmail.com>:
> Hi,
>
> Having found a posting on this list from July this year, I am trying to
> find if (and how) TRIM support is supported and enabled under RAID 1 with 2
> SSD drives.
>
> The posting was mentioned that it was included in the kernel source as of
> October 11th 2012.
>
> I see nothing on the RAID wiki for enabling TRIM for SSD backed arrays. Any
> pointers?
>
> I have a system with Debian 7 (Kernel 3.2, mdadm 3.2.5) that I am working
> on.
>
> Thanks in advance,
>
> Derek
>
> --
> Derek Piper - derek.piper@gmail.com
> --
> 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

Re: How-to for enabling TRIM for SSD RAID-1 arrays?

[Roberto Spadim]

from what i found about md raid1 support in google:

http://lkml.indiana.edu/hypermail/linux/kernel/1203.1/01772.html
[patch 4/7] md: raid 1 supports TRIM
From: Shaohua Li
Date: Sun Mar 11 2012 - 23:14:04 EST

from ext4:
https://ext4.wiki.kernel.org/index.php/Ext4_Howto#Ext4_code_implements_discard.2FTRIM
https://sites.google.com/site/lightrush/random-1/howtoconfigureext4toenabletrimforssdsonubuntu
http://forums.gentoo.org/viewtopic-p-6187612.html


2013/9/13 Roberto Spadim <rspadim@gmail.com>:
> trim is enabled at mount option of filesystem (mount -t ext4 /dev/md0
> /home -o discard)
> for ext4 it's discard option if i'm not wrong
> last kernels have trim support in software raid-1 (md raid1 driver),
> just mount the filesystem over it and use, i don't know the exact
> kernel version but it's ~1 year old feature
>
> 2013/9/13 Derek Piper <derek.piper@gmail.com>:
>> Hi,
>>
>> Having found a posting on this list from July this year, I am trying to
>> find if (and how) TRIM support is supported and enabled under RAID 1 with 2
>> SSD drives.
>>
>> The posting was mentioned that it was included in the kernel source as of
>> October 11th 2012.
>>
>> I see nothing on the RAID wiki for enabling TRIM for SSD backed arrays. Any
>> pointers?
>>
>> I have a system with Debian 7 (Kernel 3.2, mdadm 3.2.5) that I am working
>> on.
>>
>> Thanks in advance,
>>
>> Derek
>>
>> --
>> Derek Piper - derek.piper@gmail.com
>> --
>> 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



-- 
Roberto Spadim

Re: How-to for enabling TRIM for SSD RAID-1 arrays?

[Stan Hoeppner]

On 9/13/2013 3:25 PM, Derek Piper wrote:

> Having found a posting on this list from July this year, I am trying to
> find if (and how) TRIM support is supported and enabled under RAID 1 with 2
> SSD drives.

The are more important questions to first ask yourself.

1.  Will TRIM benefit your make/model of SSDs?
    Are they the same brand, model, and firmware?  If different brands
    or models, or even the same model w/different firmware, the two may
    behave completely differently WRT TRIM.  One may speed up while the
    other slows down.

2.  Will it benefit your workloads?

3.  How compressible are your files, on average?

4.  Which SSDs?  SandForce 22xx based?  Which firmware rev?  See:
http://www.anandtech.com/show/6107/corsair-force-series-gs-240gb-review

5.  Do you plan to use realtime discard or batch discard?  Most recent
    data shows that realtime discard murders performance.


Summary:  There is much, much, more to optimizing SSD performance than
getting TRIM working down the stack.  In fact some SSDs work better
without TRIM, and some perform worse when TRIM is used.

For many users, TRIM is a solution to a problem they may never have.
They simply want it because they've read somewhere that they should have it.

-- 
Stan

Re: How-to for enabling TRIM for SSD RAID-1 arrays?

[Derek Piper]

I have 2 Sandisk Extreme 120GB SSDs (Sandforce 2281 with latest
firmware - R211). I have indeed heard that TRIM was desirable to limit
the effects of write amplification and to keep the write performance
to a good level throughout the life of the drive(s). This machine is a
home file/print/web/mysql server (the real large data being on regular
7200RPM HDD RAID arrays). The SSDs are for boot, root and home
directories.

A periodic 'garbage collection' type TRIM operation would be fine, and
can be run at a cron job I see. It was not clear to me how the md-raid
went about enabling that at the device level so fstrim would even
work.

In looking over the SanDisk Extreme with SandForce stuff relating to
the firmware revision it appears that it is 5.03 or 5.04 in revision
R211. It's possible that it might just not be worth it. I had a
feeling that by enabling TRIM it would help my drives out. If that's
not the case then it may best be left alone.

Thanks,

Derek

On Fri, Sep 13, 2013 at 6:54 PM, Stan Hoeppner <stan@hardwarefreak.com> wrote:
> On 9/13/2013 3:25 PM, Derek Piper wrote:
>
>> Having found a posting on this list from July this year, I am trying to
>> find if (and how) TRIM support is supported and enabled under RAID 1 with 2
>> SSD drives.
>
> The are more important questions to first ask yourself.
>
> 1.  Will TRIM benefit your make/model of SSDs?
>     Are they the same brand, model, and firmware?  If different brands
>     or models, or even the same model w/different firmware, the two may
>     behave completely differently WRT TRIM.  One may speed up while the
>     other slows down.
>
> 2.  Will it benefit your workloads?
>
> 3.  How compressible are your files, on average?
>
> 4.  Which SSDs?  SandForce 22xx based?  Which firmware rev?  See:
> http://www.anandtech.com/show/6107/corsair-force-series-gs-240gb-review
>
> 5.  Do you plan to use realtime discard or batch discard?  Most recent
>     data shows that realtime discard murders performance.
>
>
> Summary:  There is much, much, more to optimizing SSD performance than
> getting TRIM working down the stack.  In fact some SSDs work better
> without TRIM, and some perform worse when TRIM is used.
>
> For many users, TRIM is a solution to a problem they may never have.
> They simply want it because they've read somewhere that they should have it.
>
> --
> Stan
>
>
>



-- 
Derek Piper - derek.piper@gmail.com

Re: How-to for enabling TRIM for SSD RAID-1 arrays?

[Mikael Abrahamsson]

On Fri, 13 Sep 2013, Derek Piper wrote:

> I have 2 Sandisk Extreme 120GB SSDs (Sandforce 2281 with latest
> firmware - R211). I have indeed heard that TRIM was desirable to limit
> the effects of write amplification and to keep the write performance
> to a good level throughout the life of the drive(s). This machine is a
> home file/print/web/mysql server (the real large data being on regular
> 7200RPM HDD RAID arrays). The SSDs are for boot, root and home
> directories.

You're most likely much better off by just using 80 gigs out of those 120 
gig drives (don't use all space for partition) to avoid write 
amplification.

TRIM has performance problems on some hardware (takes a long time per 
block), it's probably just better and easier to just keep blocks unused 
(never written to) and ignore TRIM.

https://en.wikipedia.org/wiki/Write_amplification#Over-provisioning

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