Strange delays in ZFS scrub or resilver

Rob Rati rob at
Sun Feb 24 15:37:01 UTC 2013

A bit of a stab in the dark here, but are any of the disks in your array Advanced Format drives?  If so, did you create a pool with a block size of 4k?  Lastly, are all the partitions on your disks (if any) aligned to 4k sector boundaries (in the case of the Advanced Format disks)?


On Feb 23, 2013, at 11:23 PM, John Levine 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.
> 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.)
> I'm running this on the console, and there are no disk error messages.
> Any idea what's going on or how to fix it?  I could move the disks to
> an ESATA enclosure if USB is losing interrupts or something.
> My recollection is that when I've done a scrub, it does the same thing,
> work, pause, work, pause.
> R's,
> John
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