I recently took over several SQL Servers that have at least 3 separate physical drive arrays that were originally used for tempdb, SQLData and SQLlogs (just like many of the systems I've supported in the past). However, sometime prior to me joining the team, the previous DBA purchased one SSD drive for each server and he moved everything to this one SSD drive including tempdb, SQLData and SQLLog files. I'm seeing significant disk IO bottlenecks. Disk Queue Lengths are through the roof during peak operations. I'm thinking I should leverage the other drive arrays to improve disk IO. My question is: Given our current config (1 SSD drive and 3 separate drive arrays (RAID10)), between tempdb, data and log, which is best suited for the SSD drive and or which should I move to the hard drives?
I would leave TempDB on the SSD and then move the Data & Log files to their own separate drive arrays. SSD's are usually good for random stuff, so TempDB is usually an excellent candidate for that type of storage media.
I would like to say that it does depend. You haven't let us know yet what the system load looks like yet. Is tempdb usage high? Are you using features that particularly tax tempdb? I agree that the data and log files should probably be separated. However, I suggest that you take a close look at wait stats and storage system usage after the change to make sure the move was a good one. Whatever you do: measure, change and re-measure to ensure the change was "good"