Date: Mon, 25 Feb 2013 09:19:28 -0500 From: Paul Kraus <paul@kraus-haus.org> To: "freebsd-questions@freebsd.org List" <freebsd-questions@freebsd.org> Subject: Re: Strange delays in ZFS scrub or resilver Message-ID: <7BEF43DD-9920-4923-BF21-A16CDD570F4C@kraus-haus.org> In-Reply-To: <20130224042340.11192.qmail@joyce.lan> References: <20130224042340.11192.qmail@joyce.lan>
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On Feb 23, 2013, at 11:23 PM, John Levine <johnl@iecc.com> wrote: > I have a raidz of three 1 TB SATA drives, in USB enclosures. One of > the disks went bad, so I replaced it last night and it's been > resilvering ever since. I can watch the activity lights on the disks > and it cranks away for a minute or so, then stops for a minute, then > cranks for a minute, and so forth. If I do a zpool status while it's > stopped, the zpool waits until the I/O resumes, and a ^T shows it > waiting for zio->io_cv. >=20 > I'm running FreeBSD 9.1, amd64 version, totally vanilla install on a > mini-itx box with 4GB of RAM. The root/swap disk is an SSD separate > from the zfs disks. When the disks are active, top shows about 10% > system time and 4% interrupt. When it isn't, top shows about 99.8% > idle. The server isn't doing much else, and nothing else currently > touches the disks. (They're for remote backup of a system somewhere > else, and I have the backup job turned off until resilvering > completes.) Under 9.0 I had some external drives attached via USB and saw = truly terrible I/O performance. I moved them to ESATA and it got much = better. Unfortunately, my external exclosure has a SATA port expander as = I need to talk to 4 external drives. That gives me about a factor of 2 = worse performance than the internal SATA drives (even if I am only = talking to one drive via the external connection). -- Paul Kraus Deputy Technical Director, LoneStarCon 3 Sound Coordinator, Schenectady Light Opera Company
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