For the most part the DBs on the server are pretty small and low usage. It's just got a couple larger databases that have pretty heavy usage. We've found when some of these DBs start working hard, while SQL is generally fine and responds without issue, it literally brings other systems sharing the same SAN to their knees. We've nailed the problem down to the controllers getting saturated with IO intensive tasks on the SQL server, and our infrastructure guys said that splitting the DBs data files specifically across multiple LUNs will help somewhat. We've had to move these DBs to internal disk until we can resolve the issue.

Tempdb is already on its own LUN with 8 data files; should I be splitting tempdb across multiple LUNs? Also, I really do mean 4 data + 1 log. Our setup has drives j,k,l,m for data and i for log, x for tempdb, d (internal) for SQL + system DBs, and e (internal) for the heavily used moved DBs (d & e are separate arrays).

Maybe what I should do is just spread the IO by adding multiple files for the DBs that are giving us headaches? But that obviously brings me back to my original query on how to spread the data evenly.

@Carl, I'm not entirely sure how to read the results of your query, but this is the main DB that is giving us problems:

IOUsageCntDBNameDbIDFileIdNumberReadsNumberWritesIoStallReadMsIoStallWriteMs

38363261AVI_DPM_Data51197955941856766738644061249515609767

10753892AVI_DPM_Data52520289102336032486994772105949