Date: Mon, 19 Dec 2011 21:42:53 +0100 From: Stefan Esser <se@freebsd.org> To: Michael Reifenberger <mike@reifenberger.com> Cc: FreeBSD Current <freebsd-current@freebsd.org> Subject: Re: Uneven load on drives in ZFS RAIDZ1 Message-ID: <4EEFA1CD.4040001@freebsd.org> In-Reply-To: <alpine.BSF.2.00.1112191724310.33692@gw.reifenberger.com> References: <4EEF488E.1030904@freebsd.org> <alpine.BSF.2.00.1112191724310.33692@gw.reifenberger.com>
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Am 19.12.2011 17:36, schrieb Michael Reifenberger: > Hi, > a quick test using `dd if=/dev/zero of=/test ...` shows: > > dT: 10.004s w: 10.000s filter: ^a?da?.$ > L(q) ops/s r/s kBps ms/r w/s kBps ms/w %busy Name > 0 378 0 0 12.5 376 36414 11.9 60.6| ada0 > 0 380 0 0 12.2 378 36501 11.8 60.0| ada1 > 0 382 0 0 7.7 380 36847 11.6 59.2| ada2 > 0 375 0 0 7.4 374 36164 9.6 51.3| ada3 > 0 377 0 1 10.2 375 36325 10.1 53.3| ada4 > 10 391 0 0 39.3 389 38064 15.7 80.2| ada5 Thanks! There are surprising differences (ada5 has a queue length of 10 and much higher latency than the other drives). > Seems to be sufficiently equally distributed for a life system... Hmmm, 50%-55% busy on ada3 and ada4 contrasts with 80% busy on ada5. > zpool status shows: > ... > NAME STATE READ WRITE CKSUM > boot ONLINE 0 0 0 > raidz1-0 ONLINE 0 0 0 > ada0p3 ONLINE 0 0 0 > ada1p3 ONLINE 0 0 0 > ada2p3 ONLINE 0 0 0 > ada3p3 ONLINE 0 0 0 > ada4p3 ONLINE 0 0 0 > ada5p3 ONLINE 0 0 0 > ... > > The only cases I've seen (and expected to see) unequal load > distributions on ZFS was after extending a nearly full four disk mirror > pool by additional two disks. In my case the pool was created from disk drives with nearly identical serial numbers in its current configuration. Some of the drives have a few more power-on hours, since I performed some tests with them, before moving all data from the old pool the new one, but else everything should be symmetric. Best regards, STefanhome | help
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