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SubjectRe: [patch v2 0/6] Add TRIM support for raid linear/0/1/10
=/ well maybe with a sas disk it could be faster? maybe a pciexpress disk too?

Em 20 de março de 2012 23:08, Shaohua Li <> escreveu:
> 2012/3/20 Shaohua Li <>:
>> 2012/3/20 Holger Kiehl <>:
>>> Hello,
>>> On Tue, 20 Mar 2012, Shaohua Li wrote:
>>>> 2012/3/20 Holger Kiehl <>:
>>>>> Hello,
>>>>> On Fri, 16 Mar 2012, Shaohua Li wrote:
>>>>>> The patches add TRIM support for raid linear/0/1/10. I'll add TRIM
>>>>>> support
>>>>>> for
>>>>>> raid 4/5/6 later. The implementation is pretty straightforward and
>>>>>> self-explained.
>>>>>> v1->v2:
>>>>>> 1. fixed a checking issue
>>>>>> 2. dropped discard request plug and replace it with no discard merege,
>>>>>> because
>>>>>> current SCSI layer can't handle discard request merge.
>>>>> Have tested TRIM patches on three different systems with the following
>>>>> hardware/ setup:
>>>>>   1) root mounted on a raid1 over two SAS SSD's (200GB) and /home
>>>>> partition
>>>>>      on a raid0 over a fusionio ioDrive Duo. Is very new and seen very
>>>>>      little usage.
>>>>>   2) root and /home mounted on a raid0 over two Intel X25 Postville
>>>>>      (160GB) connected to a Intel P55 Express chipset. Has seen very
>>>>>      heavy usage for approx. 2 years.
>>>>>   3) root and /home mounted on a raid0 over three OCZ-VERTEX2 (120GB)
>>>>>      connected via ICH7 south bridge. Has seen mild usage for approx.
>>>>>      1.5 years.
>>>>> Made the following observations when running my own benchmark which
>>>>> copies around a lot of small files and deletes them. The benchmark on
>>>>> all systems was always run only on the /home partition ie. on a raid0.
>>>>> For system 1) there is hardly any measurable differnce whether discard
>>>>> is enabled or not (~29000 files per second).
>>>>> On system 2) the performance drops from 6500->3700 files per second,
>>>>> but under normal usage one does not notice any difference.
>>>> do you have the blktrace data when the benchmark is running, especially
>>>> when doing file deletion. I'd like to check the latency of discard in this
>>>> case.
>>> It is uploaded on
>> Thanks, I'll check it.
> Thanks for the testing. The trace data is very helpful. In the intel
> SSD, trace data
> shows a discard request uses about 1 ~ 3 ms. The filesystem suffers from
> fragmentation too, so lots of small discard requests. When ext4 starts doing
> discard, it usually uses more than 1 minutes. That's too bad.
> If just looking one disk's trace data, there are some extra latencies between
> two discard requests. The combined trace data of two disks show the latency
> comes from waiting for another disk, so nothing abnormal. I thought we could
> do an optimization for this case in the future.
> So in summary, discard from the SSDs is slow. When your filesystem is
> fragmented, the performance will be terrible.
> Thanks,
> Shaohua
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Roberto Spadim
Spadim Technology / SPAEmpresarial
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