Hi Carsten, You seem to be using dd for write testing. In my testing I noted that there was a large difference in write speed between using dd to write from /dev/zero and using other files. Writing from /dev/zero always seemed to be fast, reaching the maximum of ~200MB/s and using cp which would perform poorler the fewer the vdevs.
This also impacted the zfs send speed, as with fewer vdevs in RaidZ2 the disks seemed to spend most of their time seeking during the send. On Thu, Oct 16, 2008 at 1:27 AM, Carsten Aulbert <[EMAIL PROTECTED] > wrote: > Some time ago I made some tests to find this: > > (1) create a new zpool > (2) Copy user's home to it (always the same ~ 25 GB IIRC) > (3) zfs send to /dev/null > (4) evaluate && continue loop > > I did this for fully mirrored setups, raidz as well as raidz2, the > results were mixed: > > > https://n0.aei.uni-hannover.de/cgi-bin/twiki/view/ATLAS/ZFSBenchmarkTest#ZFS_send_performance_relevant_fo > > The culprit here might be that in retrospect this seemed like a "good" > home filesystem, i.e. one which was quite fast. > > If you don't want to bother with the table: > > Mirrored setup never exceeded 58 MB/s and was getting faster the more > small mirrors you used. > > RaidZ had its sweetspot with a configuration of '6 6 6 6 6 6 5 5', i.e. > 6 or 5 disks per RaidZ and 8 vdevs > > RaidZ2 finally was best at '10 9 9 9 9', i.e. 5 vdevs but not much worse > with only 3, i.e. what we are currently using to get more storage space > (gains us about 2 TB/box). > > Cheers > > Carsten > _______________________________________________ > zfs-discuss mailing list > zfs-discuss@opensolaris.org > http://mail.opensolaris.org/mailman/listinfo/zfs-discuss >
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