Date: Mon, 19 Dec 2011 22:00:20 +0100 From: Stefan Esser <se@freebsd.org> To: Daniel Kalchev <daniel@digsys.bg> Cc: FreeBSD Current <freebsd-current@freebsd.org> Subject: Re: Uneven load on drives in ZFS RAIDZ1 Message-ID: <4EEFA5E4.9070803@freebsd.org> In-Reply-To: <83648C73-E45F-4ABA-8E83-4C8903A683AB@digsys.bg> References: <4EEF488E.1030904@freebsd.org> <83648C73-E45F-4ABA-8E83-4C8903A683AB@digsys.bg>
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Am 19.12.2011 19:03, schrieb Daniel Kalchev: > I have observed similar behavior, even more extreme on a spool with dedup enabled. Is dedup enabled on this spool? Thank you for the report! Well, I had dedup enabled for a few short tests. But since I have got "only" 8GB of RAM and dedup seems to require an order of magnitude more to be working well, I switched dedup off again after a few hours. > Might be that the DDT tables somehow end up unevenly distributed to disks. My observation was on a 6 disk raidz2. Hmmm, there was another report of even distribution of load on a 6 disk raidz1 (but in fact, in that case the first half seems to have got some 10% to 15 higher load than the second half; the sixth drive showed quite different queue length and latencies and I think these might be caused either by a defect (soft-errors) or another partition being actively used only on that drive). Regards, STefan
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