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Re: What`s wrong with JFS configuration?

From: Chris Browne <cbbrowne(at)acm(dot)org>
To: pgsql-performance(at)postgresql(dot)org
Subject: Re: What`s wrong with JFS configuration?
Date: 2007-04-25 14:46:28
Message-ID: 608xcgo6kb.fsf@dba2.int.libertyrms.com (view raw or flat)
Thread:
Lists: pgsql-performance
pawel(dot)gruszczynski(at)inea(dot)com(dot)pl (Paweł Gruszczyński) writes:
> To test I use pgBench with default database schema, run for 25, 50, 75
> users at one time. Every test I run 5 time to take average.
> Unfortunetly my result shows that ext is fastest, ext3 and jfs are
> very simillar. I can understand that ext2 without jurnaling is faster
> than ext3, it is said that jfs is 40 - 60% faster. I cant see the
> difference. Part of My results: (transaction type | scaling factor |
> num of clients | tpl | num on transactions | tps including connection
> time | tps excliding connection time)
>
> EXT2:
>
> TPC-B (sort of),50,75,13,975|975,338.286682,358.855582
> TPC-B (sort of),50,75,133,9975|9975,126.777438,127.023687
> TPC-B (sort of),50,75,1333,99975|99975,125.612325,125.636193
>
> EXT3:
>
> TPC-B (sort of),50,75,13,975|975,226.139237,244.619009
> TPC-B (sort of),50,75,133,9975|9975,88.678922,88.935371
> TPC-B (sort of),50,75,1333,99975|99975,79.126892,79.147423
>
> JFS:
>
> TPC-B (sort of),50,75,13,975|975,235.626369,255.863271
> TPC-B (sort of),50,75,133,9975|9975,88.408323,88.664584
> TPC-B (sort of),50,75,1333,99975|99975,81.003394,81.024297
>
>
> Can anyone tell me what`s wrong with my test? Or maybe it is normal?

For one thing, this test is *probably* staying mostly in memory.  That
will be skewing results away from measuring anything about the
filesystem.

When I did some testing of comparative Linux filesystem performance,
back in 2003, I found that JFS was maybe 20% percent faster on a
"write-only" workload than XFS, which was a few percent faster than
ext3.  The differences weren't terribly large.

If you're seeing such huge differences with pgbench (which includes
read load, which should be virtually unaffected by one's choice of
filesystem), then I can only conclude that something about your
testing methodology is magnifying the differences.
-- 
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