I am a database consultant for an imaging software vendor. Many of our customers are moving to SAN solutions to store our software's SQL database and we've often received calls regarding performance issues after this migration. It seems that many of the customer's DBA's don't put much thought into the I/O tuning aspect and the underlying RAID configuration performance benefits. They simply create a large RAID group with a pool of storage that can be allocated to different LUN's. Most recently, this was case with a customer of ours. They had one large Raid 5 group (30 disks) behind one perc fibre channel controller (1 channel) connected to EMC San Storage unit. This group was broken out into 3 LUN's. These 3 LUN's were then seen as 3 separate physical disks through Windows. However, they decided that it would be easier to manage this storage by taking these 3 physical drives and creating a dynamic spanned volume equating to one logical (E<img src='/community/emoticons/emotion-1.gif' alt='' /> drive letter. I had a surprisingly hard time convincing them that this was a bad idea, but I also don't know enough about SAN storage to provide substantial factual evidence. Perfmon showed average disk queue lengths that were significantly high for long periods of time, so this helped in proving my case.