We recently, last week, migrated the bulk of our servers to ESX 3.5. Upon doing so, users are now timing out when using database intensive applications. Given our main database server was previously connected to a SAN with 10k U320 drives, why would it perform poorer on the same SAN now using 15k U320 drives? I have even moved the VM in question onto local storage, 10k SAS drives, which works fine for a few hours, but users are timing out again. I am going to perform some maintenance on the VM running MS SQL 2k to hopefully help disk I/O, but what else might be causing this performance hit?