[Lustre-discuss] Bad read performance

[Alvaro Aguilera]

no, for the time being I'm stuck with this version...

Regards,
Alvaro.

On Fri, Aug 21, 2009 at 4:57 AM, Oleg Drokin <Oleg.Drokin at sun.com> wrote:

> Hello!
>
>   Any chance you can use more modern release like 1.8.1? There was a number
> of bugs fixed including some readahead-logic fixes that could impede read
> performance.
>
> Bye,
>    Oleg
>
> On Aug 20, 2009, at 10:38 PM, Alvaro Aguilera wrote:
>
>  Thanks for pointing that out. I was using the default striping, which in
>> my case is 1mb stripes, on one OST.
>>
>> However,  If I change the stripe size to 32mb (the size of the buffers
>> being written/read), the function used to write the file using O_DIRECT
>> stops working. Its code is very similar to the one posted above and the
>> problem is that the write()-function stucks while writing the first buffer.
>> Is there any trick for using O_DIRECT in Lustre? I've aligned the buffer
>> using posix_memalign(), and every offset and count seem to be a multiple of
>> the page-size (4kb).
>>
>>
>>
>>
>>
>> On Fri, Aug 21, 2009 at 12:04 AM, Brian J. Murrell <Brian.Murrell at sun.com>
>> wrote:
>> On Thu, 2009-08-20 at 23:52 +0200, Alvaro Aguilera wrote:
>> > I'm facing the following problem: when this code is run in parallel
>> > the read operations on certain processes start to need more and more
>> > time to complete. I attached a graphical trace of this, when using
>> > only 2 processes.
>>
>> Just a (perhaps silly) question, but does the striping of the file (or
>> the directory the file is being created in) on the filesystem match your
>> I/O patterns?  That is, ideally, each thread/rank/process (whatever you
>> want to call them) should be doing I/O in it's own stripe.
>>
>> $ man lfs
>>
>> if none of this is meaningful.
>>
>> b.
>>
>>
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>
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