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[oracle-l] Re: Help With Veritas and my search for the Holy "I/O" Grail (testing with the tool from

From: Jonathan Lewis <>
Date: Sun, 25 Jan 2004 12:00:57 -0000
Message-ID: <011901c3e33a$e911ebe0$6702a8c0@Primary>

I haven't tried running iozone, so I don't know what the default output looks like so this question may be irrelevant, but are you checking the O_SYNC figures against Oracle's performance (iozone option -o) ?

If not, then you're not comparing like with like.


Jonathan Lewis

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We have been trying to squeak out a little bit more bandwidth from our disk sub-system. I have been doing benchmarks using the tool from The command I use for the basic baseline test is
"iozone -Rab base.wks" which in effect takes all system default values to
do the reads/writes. I then test with the command "iozone -IRab vx_direct.wks" which now forces the reads/writes to direct I/O by issuing the command "ioctl(fd,VX_SETCACHE,VX_DIRECT);" in the .c program. When we compare the performance of the base to the direct timings it's like "WOW, Where have you been all my life".

So now we are puzzled as to just how in the 'el do we get Oracle to use the direct option. We have read the Veritas manuals and combed several pages on (Steve Adam's site). The mount options/combinations we have tried are "mincache=direct,convosync=direct" and
"convosync=direct,mincache=dsync". The base line testing with iozone is
between 50 and 100 percent slower with either of these mount options in place. Running iozone with the "-I" (vx_direct enabled) continues to scream regardless of what we do to the mount points.

So now, WTF do I do.

PS: The first person who suggests raw disk or QIO has to find me a shrubbery) Received on Sun Jan 25 2004 - 06:00:57 CST

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