Is NCQ supported when setting the controller to JBOD instead of using HW raid? On 3/5/06, Eric D. Mudama <edmudama@xxxxxxxxx> wrote: > On 3/4/06, Steve Byan <smb@xxxxxxxxxxx> wrote: > > On Mar 4, 2006, at 2:10 PM, Jeff Garzik wrote: > > > Measurements on NCQ in the field show a distinct performance > > > improvement... 30% has been measured on Linux. Nothing to sneeze at. > > > > Wow! 30% is amazing. I'd be interested in knowing how the costs break > > down; are these measurements published anywhere? > > Full-stroke random reads with small operations (4k or less) typically > show 75-85% performance improvement, from the ability of a 7200rpm > drive to carve 4ms out of their response time, as well as a huge chunk > of seek distance. > > Random writes, since as you said they're already reordered with cache > enabled, don't typically show any sort of increase in desktop > applications. > > NCQ FUA writes or NCQ writes with cache disabled should show the same > ballpark performance improvement as random reads in saturated > workloads. Again however, this is for the full-stroke random case. > Local area workloads need to be analyzed more thoroughly, and may > differ in performance gain by manufacturer. > > --eric > -- Raz - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
