Test results for ext4

[Valerie Clement <valerie.clement@bull.net>]

Hi all,

Since a couple of weeks, I did batches of tests to have some performance
numbers for the new ext4 features like uninit_groups, flex_bg or
journal_checksum on a 5TB filesystem.
I tried to test allmost all combinations of mkfs and mount options, but
I put only a subset of them in the result tables, the most significant
for me.

I had started to do these tests on a kernel 2.6.26-rc1, but I'd got several
hangs and crashes occuring randomly outside ext4, sometimes in the slab
code or in the scsi driver eg., and which were not reproductible.
Since 2.6.26-rc2, no crash or hang occur with ext4 on my system.

The first results and the test description are available here:
http://www.bullopensource.org/ext4/20080530/ffsb-write-2.6.26-rc2.html
http://www.bullopensource.org/ext4/20080530/ffsb-readwrite-2.6.26-rc2.html

I will complete them in the next days.

In the first batch of tests, I compare the I/O throughput to create
1-GB files on disk in different configurations. The CPU usage is also
given to show mainly how the delayed allocation feature reduces it.
The average number of extents per file shows the impact of the
multiblock allocator and the flex_bg grouping on the file fragmentation.
At last, the fsck time shows how the uninit_groups feature reduces the
e2fsck duration.

In the second batch of tests, the results show improvements in transactions
-per-second throughput when doing small files writes, reads and creates
when using the flex_bg grouping.
The same ffsb test on an XFS filesystem hangs, I will try to have traces.

If you are interested in other tests, please let me know.

   Valérie


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