On Fri, Jan 8, 2010 at 1:44 PM, Ian Collins <i...@ianshome.com> wrote:
> 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. >> >> >> > What is you data? > > I have seen the same, fsstat reports 4-7 seconds of small writes then bursts of 40-80MB/s but without dedup i see 80-150MB/s writes on my 4x 500GB sata drives, split between two controllers. 6GB of ram, and about 1.5TB of storage with 1.2TB used. if I disable dedup, speed goes backup. While doing dedup writes zfs destroy pool/filesystem takes about 100x time as usual even if the pool is that is being destroyed is empty reports say its far worse when over 100GB of data is on a drive. my dedup ratio for the pool is 1.15x. Read performance seems about the same or slightly faster I didn't really benchmark this work load since my clients seem to be the bottleneck. As money is tight at the moment i don't have the funds for a SSD to test with, but have disk space on non-utilized disk to try but haven't researched the effect of adding and removing (if possible) l2arc or zil log slices on a pool. it would be great to enable a 5-50GB slice off a sata drive to use as logging device for greater performance. James Dickens uadmin.blogspot.com I've found data that lends its self to deduplication writes slightly faster > while data that does not (video, iso images) writes dramatically slower. So > I turn dedupe (and compression) off for filesystems containing "random" > data. > > -- > Ian. > > > _______________________________________________ > zfs-discuss mailing list > zfs-discuss@opensolaris.org > http://mail.opensolaris.org/mailman/listinfo/zfs-discuss >
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