Just how much your disk subsystem performance will improve using the tuning techniques that I've described in this article depends on your environment. To test the differences in matching the allocation unit size, I ran a stress test. My test system consisted of an NT Server 4.0 file server configured with a 100BASE-T network card, a 200MHz Pentium Pro processor, 64MB of RAM, a SCSI-based hardware RAID array controller with 16MB of onboard cache, a hard disk for NT, a hard disk for the paging file, and a three-disk RAID 5 array. I tested this system by using the Dynameasure file-server stress-testing tool from Bluecurve operating from four 400MHz Pentium II processor clients with 128MB of RAM and 100BASE-TX networking cards.
While running the baseline test, I used Performance Monitor to obtain the disk characteristics of the RAID 5 array. I used this information to reformat the RAID 5 array from the default allocation unit size of 4KB to an allocation unit size of 64KB according to my Performance Monitor results. When I retested the system with the same workload, the results were dramatic,. once the load increased on the file server, the performance of the tuned RAID array improved by more than 5Mbps, in some instances!