[Lustre-discuss] Lustre write performances 4 times faster after removing SD_IOSTATS from kernel

[Charland, Denis]

After performing some tests, I noticed that after removing SD_IOSTATS functionality from the
kernel, the write performances of Lustre was 4 times faster. On a Lustre 1.8.7 client, I untared a tarfile
of a directory containing about 225,000 files (6.4GB). I used time to measure the time it takes to perform
the operation. I performed the tests with two Lustre 1.8.7 servers with identical hardware. One is running
Fedora 12 with a 2.6.32-19 patched kernel and the other one is running Fedora 7 with a 2.6.22-14 patched kernel.
With both servers, it took about 4 minutes to untar the tarfile when running the kernel without SD_IOSTATS
compared to about 16 minutes when running the kernel with SD_IOSTATS.

Is that normal that SD_IOSTATS has a so big impact on Lustre write performances?

Denis Charland
UNIX Systems Administrator
National Research Council Canada
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