Having a weird issue on my Dell PS6100.

I've got about 6 volumes on it. I have a test VM I'm working with, Server 2008 with nothing installed on it. If I migrate the VM to the very first volume I ever created and run CrystalDiskMark on it, I get about 300-400MB/s read and about 250-350MB/s write on a sequential test.

If I migrate it to any other volume on my SAN, regardless of how full it is (I even created a new one and inherited all permissions and set settings identical to the 1st volume), this drops to 100-150MB/s read and about 80-120MB/s write.

If I migrate it back to the 1st volume, speeds return to normal.

I have also tried deleting the VM and recreating it on another volume just in case it had something to do with where the VM originated and no luck. I can create it on Volume 5, bad performance. Move it to volume 1, good performance. Create it on Volume 1, good performance, move it to volume 3, bad performance.

Any ideas?