Hello, We have a strange problem and I can not figure out what is causing it. About every 20 min (sometimes 25 sometimes 15 min) we have a performance problem. The Write Disk Queue Length exceeds 200 at that time for about 30 sec. We can however not find any query that is writing more than normal during that time (checked with profiler). All other counters are fine, the Buffer Cache Hit Ration is over 99.6% The machine we are using is a Dell Poweredge 4 CPU; Raid 10 for the data and Raid 1 for the transaction log. What can cause this enormous queue length?