[Lustre-discuss] Curious about iozone findings of new Lustre FS

[Jagga Soorma]

Hi Guys,

(P.S. My apologies if this is a duplicate - Sent this email earlier today
with an attachment and did not see it populate in google groups so was not
sure if attachments were allowed)

I have just deployed a new Lustre FS with 2 MDS servers, 2 active OSS
servers (5x2TB OST's per OSS) and 16 compute nodes.  It looks like the
iozone throughput tests have demonstrated almost linear scalability of
Lustre except for when WRITING files that exceed 128MB in size.  When
multiple clients create/write files larger than 128MB, Lustre throughput
levels up to approximately ~1GB/s. This behavior has been observed with
almost all tested block size ranges except for 4KB.  I don't have any
explanation as to why Lustre performs poorly when writing large files.

Here is the iozone report:
http://docs.google.com/fileview?id=0Bz8GxDEZOhnwYjQyMDlhMWMtODVlYi00MTgwLTllN2QtYzU2MWJlNTEwMjA1&hl=en

The only changes I have made to the defaults are:
stripe_count: 2 stripe_size: 1048576 stripe_offset: -1

I am using Lustre 1.8.1.1 and my MDS/OSS servers are running RHEL 5.3.  All
the clients are SLES 11.

Has anyone experienced this behaviour?  Any comments on our findings?

Thanks,
-J
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