Re: Tuning ZFS: performance anomaly with nocacheflush

Hi Charles,

I asked one of the zfs experts and his comment was:

   nocacheflush shouldn't be a problem since S10u5. If they are on    S10u4 or u3 (ack!) then they are probably hitting one or more of    other known problems, long since fixed.

So check what version of Solaris you're running and you may need to upgrade.

Regards,

Dave Miller

Charles Schultz wrote, On 11/18/08 09:44:
> Good day list,
>
> We are investigating why turning on the ZFS nocacheflush would affect a
> simple (traditional) import so drastically. With the nocacheflush
> default (0), we observe normal behavior. With the nocachflush set to 1,
> we observe each db writer process suddenly having a LWP (Lightweight
> Process) count in excess of 150 (some up to 175). This caused
> significant kernel contention and slowed down the import significantly.
> A truss on dbwr processes shows lots of sleeping and lwp_parking. I was
> not able to find much relevant information on google or metalink for
> tags "oracle zfs nocacheflush". Any ideas?
>
> Oracle EE 10.2.0.2 <http://10.2.0.2> on Solaris 10, hardware is Sun
> T5240, EMC C3-80 SAN.
>
> --
> Charles Schultz

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