Reading Microsoft recommendation, the latency (sec/read or sec/write) for the Exchange database disk (separated from the transaction log disk) should not go above 40 ms average and 100 ms for spike. On my Exchange 2003 server I?m getting 122 ms for the average and 257 ms for the spike. The disk subsystem in my environment includes: two FC HBA?s, each connected using FC cables to a controller ( one HBA to one controller, total of two sets) on an FC disk array (Raidsys). On the FC disk array I have two LUN each with RAID 5 and each LUN expose via one controller ( total of two LUN). From the server side the OS seas two disks, one for the database and one for the transaction log. Am I?m doing something wrong?