ODM Performance Question

[ALORA]

 Hi,

After switching from node A to node B in a 2-node oracle 9i database cluster, we noticed that our transactions were taking

much longer to complete, with very high I/O waits and high CPU utilization.

Upon further investigation I realized that node B with issues was configured to use the Veritas ODM drivers, while the

good node A was using the default Oracle ODM driver.

After we switched back to node A everything started runing OK.

(Node-A)# ls -l libod*lrwxrwxrwx 1 root other 11 Jul 30 2007 libodm9.so -> libodmd9.so-rw-rw-r-- 1 oracle trpdba 6532 Aug 14 2006 libodmd9.so(pidwinv-n1)#  (Node-B)# ls -l libod*lrwxrwxrwx 1 oracle trpdba 26 Sep 12 2007 libodm9.so -> /opt/VRTSodm/lib/libodm.so-rw-rw-r-- 1 oracle trpdba 6532 Aug 14 2006 libodmd9.so.od 

Contrary to what we had been told, you would think that the Veritas ODM driver would give us better performance.

Thanks

Configuration:

Solaris 9

Oracle 9.2.0.8

Sun V890

Two Node Cluster

Veritas Storage Foundation HA for Oracle 5.0 MP1

VXVM, VCS , VXFS with Q/IO enabled

[George_Lombard]

It's interesting indeed. Why don't you formally log a case with Symantec Tech Support to find out what exactly is happening. I'm sure they could come up with some performance tuning recommendation or would be interested to see the cause of this major performance difference.

[Antony_Pavlenko]

Hello.

It looks like expected behavior. Here is some assumptions.

Veritas ODM gives to you "like row device performance" with all negatives and positives.

I think your DB is read aggressive, not write (OLAP?).

I think if you will look to yours statspacks you will see significant improvement in write operations. But, I think, your read operations become worse with ODM.

So than you DB works with out of veritas ODM you heavily use file system cache and it helps a lot with read operations. But than you enable veritas ODM you read directly from disk, with out of this case, so service time and amount of read operations go up.

For this type of load ODM isn't the best choice. It can be enabled and be useful, but after rather big DB enhancements.