On Fri, Jan 08, 2010 at 10:00:14AM -0800, James Lee wrote: > I haven't seen much discussion on how deduplication affects performance. > I've enabled dudup on my 4-disk raidz array and have seen a significant > drop in write throughput, from about 100 MB/s to 3 MB/s. I can't > imagine such a decrease is normal.
Seems like I've seen other posts with similar numbers (maybe 9MB/s or so?). Sounded like adding SSD for caching really improved performance however. > > > # zpool iostat nest 1 (with dedup enabled): > > ... > > nest 1.05T 411G 91 18 197K 2.35M > > nest 1.05T 411G 147 15 443K 1.98M > > nest 1.05T 411G 82 28 174K 3.59M > > > # zpool iostat nest 1 (with dedup disabled): > > ... > > nest 1.05T 410G 0 787 0 96.9M > > nest 1.05T 410G 1 899 253K 95.0M > > nest 1.05T 409G 0 533 0 48.5M > > I do notice when dedup is enabled that the drives sound like they are > constantly seeking. iostat shows average service times around 20 ms > which is normal for my drives and prstat shows that my processor and > memory aren't a bottleneck. What could cause such a marked decrease in > throughput? Is anyone else experiencing similar effects? > > Thanks, > > James Ray _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
