[Users] discard support for SSD in OpenVZ kernel

[spameden]

I guess I hit this bug:

http://bugs.centos.org/view.php?id=6548

so hopefully it will be fixed sometime soon and include in OpenVZ

can't really migrate to XEN right now yet due lack of knowledge and very
used to OpenVZ.


2013/8/28 spameden <spameden at gmail.com>

>
>
>
> 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?
>
>
>
>>
>>
>>
>>
>> 2013/8/27 spameden <spameden at gmail.com>
>>
>>>  is it implemented?
>>>
>>>  I've tried on 3.2.0-4 debian wheezy default kernel it's working just
>>> fine:
>>> # dmsetup table
>>> vg0-home: 0 443277312 linear 9:1 25166208
>>> home: 0 443273216 crypt aes-cbc-plain
>>> 0000000000000000000000000000000000000000000000000000000000000000 0 253:2
>>> 4096 1 allow_discards
>>>
>>> But not on OpenVZ's 2.6.32.xxxx:
>>> # dmsetup table
>>> vg0-home: 0 443277312 linear 9:1 25166208
>>> home: 0 443273216 crypt aes-cbc-plain
>>> 0000000000000000000000000000000000000000000000000000000000000000 0 253:2
>>> 4096
>>> vg0-swap: 0 4194304 linear 9:1 20971904
>>> vg0-root: 0 20971520 linear 9:1 384
>>>
>>>
>>>
>>>
>>
>>
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