Tuning ZFS: performance anomaly with nocacheflush

From: Charles Schultz <sacrophyte_at_gmail.com>
Date: Tue, 18 Nov 2008 09:44:12 -0600
Message-ID: <7b8774110811180744x1721cdfct87fd8c0d0a92e090@mail.gmail.com>

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 on Solaris 10, hardware is Sun T5240, EMC C3-80 SAN.

Charles Schultz

Received on Tue Nov 18 2008 - 09:44:12 CST

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