[Users] discard support for SSD in OpenVZ kernel

[spameden]

2013/8/29 Kirill Korotaev <dev at parallels.com>

> I also want to add that SSD models referred to in  the bug (like OCZ one)
> are not server grade and you guys risk very much loosing your data or
> corrupting file system on power failure.
> You should test it heavily.
>

Thanks for that.

But we are not using OCZ (also know they are not reliable).

The SSD in this server is INTEL SSDSC2CW240A3.

I can't try the latest redhat kernel on this system, because after
converting it to deb it seems to be not working.

But I believe fix should be in 2.6.32-358.18.1.el6.centos.plus.x86_64.

>
> On Aug 29, 2013, at 03:52 , Kir Kolyshkin <kir at openvz.org> wrote:
>
>  On 08/28/2013 06:34 AM, spameden wrote:
>
>
>
>
> 2013/8/28 Kir Kolyshkin <kir at openvz.org>
>
>>  On 08/27/2013 08:20 AM, spameden wrote:
>>
>>  ArchLinux wiki says:
>> *Warning: *Users need to be certain that kernel version 2.6.33 or above
>> is being used AND that their SSD supports TRIM before attempting to mount a
>> partition with the discard flag. Data loss can occur otherwise!
>>
>>  So I guess it's not in the OpenVZ kernel?
>>
>> I'd like to use TRIM because it increases performance to SSD drastically!
>>
>>
>>  You'd better check it with Red Hat, looking into their RHEL6
>> documentation.
>>
>> My quick googling for "rhel6 kernel ssd discard" shows that rhel6 kernel
>> do support trim, they have backported it (as well as tons of other stuff,
>> so this is hardly 2.6.32 kernel anymore).
>>
>
>  I've just tested via hdparm (ofc it's not a perfect tool to test out
> disk performance but still), here is what I get on the latest
> 2.6.32-042stab079.5:
>
> # hdparm -t /dev/mapper/vg-root
> /dev/mapper/vg-root:
>  Timing buffered disk reads: 828 MB in  3.00 seconds = 275.56 MB/sec
>
>  on standard debian-7 kernel (3.2.0-4-amd64):
> # hdparm -t /dev/mapper/vg-root
> /dev/mapper/vg-root:
>  Timing buffered disk reads: 1144 MB in  3.00 seconds = 381.15 MB/sec
>
>  and it's only read speed test.
>
>  I don't get why it differs so much?
>
>
> My suggestion is, since this functionality is not directly related to
> OpenVZ, and
> we usually don't change anything in this code (unless there is a reason
> to), to
> try reproducing it on a stock RHEL6 kernel and, if it is reproducible,
> file a bug
> to red hat or, if it's not reproducible, file a bug to openvz.
>
> Kir.
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