Re: Direct I/O on vxfs on EMC

Hi

Try adding convosync=direct to /etc/vfstab for the file systems. This tells veritas to use direct I/O.

cheers

Pete Finnigan
www.pentest-limited.com

In article <3B7D71A8.6CC0_at_yahoo.com>, Connor McDonald <connor_mcdonald_at_yahoo.com> writes
>Just curious if anyone's come across this before. Got an
>email from a friend who's just put an (8i) database
>with everything (excepting the redo logs) on one large
>vxfs stripe on top of EMC disks (is standard raid-1
>config). The redos are on separate raid-1 (vxfs on
>EMC) disks.
>
>When the file systems are mounted for direct I/O - all
>the machine level stats (sar/iostat/vxstat) look fine
>but the users are up in arms about performance. The
>only sign of problems is that fibre interface to the
>disks is showing 1500 io's/sec.
>
>Mount the file systems as per normal (ie without
>direct io), and users are much happier, the fibre
>shows 120 io's/sec.
>
>Unfortunately I've just finished at the site - so I
>can't run any diagnostics. I'm guessing that maybe
>their Oracle buffer cache is way undersized, or their
>is some problems with the direct IO on EMC disks (or
>the EMC cache), but I'd appreciate any other theories...
>
>
>Cheers
>Connor
>
>

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Pete Finnigan
IT Security Consultant
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