There are so many things to consider in a SAN environment. Are you using a fiber or iSCSI connection? If it’s fiber, what topology was implemented in the fiber switch? What’s the RAID configuration, how many other systems are accessing the same controllers/disks, how many controllers vs how many disks, what types of disks?
A SAN typically has other systems besides SQL Server which contribute to I/O activity or bandwidth limitations over the fiber/iSCSI channel. If you want to measure the bandwidth of your fiber or iSCSI channel, there are is which can do this. Block Storage Tester (BST), such as Spirent SmartBits, will measure all sorts of things, but you’ll pay roughly $4000 for the software. There's also a good chance the management software included with the SAN has a tool to do this.
If you're having performance issues, there's a range of possibilities. So much of it comes down to the initial setup in hardware and configuration.
First, I would look in Windows performance monitor to check the basics, like disk I/O read/write and waits/queue length, memory, and SQL Buffer Manager to see if you can get an idea of where the bottleneck is.
If you have some other questions, it will be easier if you can provide more information on your SAN configuration, your environment, and any specifics on the performance issues.
- Dana Rivkind