Shapor Naghibzadeh wrote: > On Wed, Nov 07, 2007 at 04:42:59PM -0600, Eric Sandeen wrote: >> Again this was on a decent HW raid so seek penalties are probably not >> too bad. > > You may want to verify that by doing a benchmark on the raw device. I > recently did some benchmarks doing random I/O on a Dell 2850 w/ a PERC > (megaraid) RAID5 w/ 128MB onboard writeback cache and 6x 15krpm drives > and noticed appoximately one order of magnitude throughput drop on > small (stripe-sized) random reads versus linear. It maxed out at ~100 > random read IOPs or "seeks/sec" (suprisingly low). > > Out of curiousity, how are you counting the seeks? Chris Mason's seekwatcher (google can find it for you) is doing the graphing, it uses blocktrace for the raw data. -Eric > Shapor - To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
