From: Bernd Melchers (melchers_at_CIS.FU-Berlin.DE)
Date: Tue Aug 28 2007 - 10:23:00 CEST
Date: Tue, 28 Aug 2007 10:23:00 +0200 From: Bernd Melchers <melchers@CIS.FU-Berlin.DE> Message-ID: <20070828082300.GB2615406@CIS.FU-Berlin.DE> Subject: Re: [suse-sles-e] Slow direct I/O performance SLES 10 SP1
> I use directIO with SLES9 SP3 (and oracle) all the time, without any
> problems. Why do you think that it's broken?
I was directed by my vendor (SGI) to use directIO for streaming backup data
from raid to all of my four Ultrium2-Tape Drives. This was supposed to be
more CPU efficient than bufferedIO.
But the transfer rates were too slow with directIO (7-22 MB/sec per drive).
Then it was said, directIO is broken in SLES9 and i should switch back to
bufferedIO, at least until SLES10. With bufferedIO the transfer rates
increases to 30-90 MB/sec per Ultrium2-drive, depending on compressability
of data.
HBA Cards are qlogic12160 and LSI53C1030 (LVD160, no Fiberchannel), cpus are
itanium2.
I don't see any reason for these bad directIO transfer rates.
mit freundlichen Grüßen
Bernd Melchers
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