[Users] discard support for SSD in OpenVZ kernel

[spameden]

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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