VA7100 Queue Full Threshold

[Denver Osborn]

Would someone please explain the Queue Full Threshold for me on a VA7100 controller. The default is 750, but I've seen an HP Doc stating the VA7100 shouldn't exceed 240... then I found a service note (for va74xx) that said 750 is too high for most customers and it should be tuned using the "2*(# disks in RG) / (controller host ports)" formula. To say the least, having multiple sources from HP that suggest such a broad range is confusing. When would I go with 750, 240 or use the much lower value from the forumula? Are there any performance metrics on the VA that should be used when tuning QFT?

My VA's are in a small environment, approx 6 - 10 host hba ports with 10 to 25 or more luns in use. No multi-pathing driver, just LVM w/ PV Links on 11i v1.

Thanks in advance for the feedback

-denver