Why would a heavily disk intensive application run faster on a SAN than on a Physical Disk? I would have expected the Physical disk to be slightly faster but in fact the process ran 100 times faster when it's work drive was set to a partition on the SAN.
Our guess is that the SAN is optimised out of the box to be fast whereas the physical disk tuning settings are OS (Solaris) related and have not been touched or the OS patched.
During the highest activity the disk I/O was running at 100% and the time to complete a write was over 2 seconds as several processes were writing to the disk at the same time.
(FYI the application involved was Informatica PowerCenter)
Best Answer
I'm not at all surprised. SAN arrays typically have a LOT of disks involved. The limiting factor for disk I/O is the speed of the individual disk, and these stack. 6 drives locally in a RAID10 will perform better than 2, and 80 drives on a SAN will perform better than 10 drives locally. There are variables of course, but that's how it's supposed to work.
Also, if the SAN has any SSDs involved, things get really zippy.