[Lustre-discuss] Performance Drop creating big files
Jason Rappleye
jason.rappleye at nasa.gov
Sat May 31 00:18:40 PDT 2008
Hi Roger,
This sounds terribly familiar. The likely cause can be found by
reading through the following thread:
http://lists.lustre.org/pipermail/lustre-discuss/2008-March/007024.html
Note that running dumpe2fs on each device, as suggested by one of the
messages in the thread, did *not* result in a performance improvement.
j
On May 30, 2008, at 1:25 PM, Roger Spellman wrote:
> I am seeing the following odd behavior. I have several OSSes, each
> with a 7T RAID 5.
>
>
>
> If I use a single client to create a single 1T file which is
> striped to a single OST, the performance starts off at about 400 MB/
> s (which is typical for my HW), then gradually decreases, until it
> reaches 250 MB/s. I’ve seen this with both IOZone and dd.
>
>
> As an experiment, I wrote a script that creates two hundred 10G
> files, without removing them. Again, the performance starts off at
> 400 MB/s. But, the performance stays nearly the same throughout
> the test.
>
>
>
> The only difference between these tests is that in the second case,
> there are lots of opens & closes, and in the first case, just a
> single open and close.
>
>
>
> Can anyone explain what is happening here, and how to possible fix it?
>
>
>
> Thanks.
>
>
>
> Roger Spellman
>
> Sr. Staff Engineer
>
> Terascala, Inc.
>
>
>
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--
Jason Rappleye
System Administrator
NASA Advanced Supercomputing Division
NASA Ames Research Center
Moffett Field, CA 94035
jason.rappleye at nasa.gov
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