From: Bruce Momjian <bruce@momjian.us>
To: RBN <rbn.ggl@gmail.com>
Cc: pgsql-admin@postgresql.org
Subject: Re: fsync tests
Date: Thu, 10 Jun 2010 18:15:29 -0400 (EDT)
Message-ID: <201006102215.o5AMFTA19322@momjian.us> (raw)
In-Reply-To: <AANLkTilma41XqdLfA-yCaUQCUfC5u8wDGOGzWnY2R8jN@mail.gmail.com>
RBN wrote:
> I ran test_fsync on a local ext 3 partition and on a raid jfs SSD array
> 8x32GB RAID10. The local disk returned quickly and gave what looks like
> acceptable results. However, the RAID looks pretty bad. Any one have any
> idea why fsync would take so long on an SSD RAID 10.
As the original author of the test, all I can say is that those numbers
look bad. :-(
---------------------------------------------------------------------------
>
>
> LOCAL DISK
> Simple write timing:
> write 0.005460
>
> Compare fsync times on write() and non-write() descriptor:
> (If the times are similar, fsync() can sync data written
> on a different descriptor.)
> write, fsync, close 0.072429
> write, close, fsync 0.075627
>
> Compare one o_sync write to two:
> (o_sync unavailable)
> (o_dsync unavailable)
> write, fdatasync 0.075907
> write, fsync, 0.076320
>
> Compare file sync methods with 2 8k writes:
> (o_dsync unavailable)
> write, fdatasync 0.108367
> write, fsync, 0.108659
>
>
>
> RAID 10 SSD jfs
> Simple write timing:
> write 0.004843
>
> Compare fsync times on write() and non-write() descriptor:
> (If the times are similar, fsync() can sync data written
> on a different descriptor.)
> write, fsync, close 95.546382
> write, close, fsync 51.407276
>
> Compare one o_sync write to two:
> (o_sync unavailable)
> (o_dsync unavailable)
> write, fdatasync 10.999764
> write, fsync, 80.696959
>
> Compare file sync methods with 2 8k writes:
> (o_dsync unavailable)
> write, fdatasync 111.931881
> write, fsync, 99.329298
--
Bruce Momjian <bruce@momjian.us> http://momjian.us
EnterpriseDB http://enterprisedb.com
+ None of us is going to be here forever. +
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To: pgsql-admin@postgresql.org
Cc: bruce@momjian.us, rbn.ggl@gmail.com
Subject: Re: fsync tests
In-Reply-To: <201006102215.o5AMFTA19322@momjian.us>
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