On Sat, 26 Jul 2008, Bob Friesenhahn wrote: > I suspect that the maximum peak latencies have something to do with > zfs itself (or something in the test program) rather than the pool > configuration.
As confirmation that the reported timings have virtually nothing to do with the pool configuration, I ran the program on a two-drive ZFS mirror pool consisting of two cheap 500MB USB drives. The average latency was not much worse. The peak latency values are often larger but the maximum peak is still on the order of 9000 microseconds. I then ran the test on a single-drive UFS filesystem (300GB 15K RPM SAS drive) which is freshly created and see that the average latency is somewhat lower but the maximum peak for each interval is typically much higher (at least 1200 but often 4000). I even saw a measured peak as high as 22224. Based on the findings, it seems that using the 2540 is a complete waste if two cheap USB drives in a zfs mirror pool can almost obtain the same timings. UFS on the fast SAS drive performed worse. I did not run your program in a real-time scheduling class (see priocntl). Perhaps it would perform better using real-time scheduling. It might also do better in a fixed-priority class. Bob ====================================== Bob Friesenhahn [EMAIL PROTECTED], http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/ _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
