[lustre-discuss] strange time of reading for large file

[Dilger, Andreas]

On Nov 23, 2017, at 11:52, Rosana Guimaraes Ribeiro <rosana_guimaraes_ at hotmail.com> wrote:
> 
> Hi,
> 
> I have some doubts about Lustre, I already sent my issues to forums but no one answer me.
> In our application, during the performance testing on lustre 2.4.2 we got times of reading and writing to test I/O operations with a file of almost 400GB. 
> Running this application a lot of times, consecutively, we see that in write operations, I/O time remain on same range, but in read operations there are a huge difference of time.

I would really suggest to upgrade to a newer version of Lustre.  There have
definitely been a lot of IO performance improvements since 2.4.2.

> As you can see below:
> Write time [sec]:
> 325.77
> 318.80
> 325.44
> 458.54
> 316.89
> 327.75
> 344.90
> 340.34
> 383.57
> 316.35
> Read time [sec]:
> 570.48
> 601.11
> 447.14
> 406.39
> 480.44
> 5824.40
> 299.40
> 293.54
> 1049.93
> 4190.47
> We ran on the single client with 1 process and tested on same infrastructure (hardware and network).
> Could you explain why is reading time so distorted? What kind of problem might be occurring?
> 
> Regards,
> Rosana
> 
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Cheers, Andreas
--
Andreas Dilger
Lustre Principal Architect
Intel Corporation