Dear all,

recently we've been confronted with a problem with an Oracle database (11) running on AIX connected to an IBM DS8K array that has to be migrated to Symm DMX4. It is very sensitive to response times - should not exceed 4ms. Another must is the synchronous replication. In the current state on DS8K array it performs brilliant with RT of 2 ms. Our first tests for migration however revealed unacceptable performance on DMX - about 6 ms. In split SRDF pairs mode the there is 3 times improvement.

We thought that the reason might be the one outstanding IO per queue and the serializetion done by the SRDF. Therefore we tested peresenting directly hypers to the OS and using LVM on OS level rather than using Meta devices. We didn't get conclusive results though, despite experimenting with differen LVM stripe sizes.

Our observation is that the majority of that critical DB transactions are 8KB. And the problem with this DB is the logging - the writes.

Has anyone bumped into such problems? Is such RT of 3 ms feasible at all on DMX? Any best practices?

Thanks in advance