Swap on ZFS / swap_pager: indefinite wait buffer

[Sergey Kandaurov]

On 2 April 2012 22:13, bsalinux at gmail.com <bsalinux at gmail.com> wrote:
> Hi,
>
> I have been running FreeBSD 9.0-RELEASE from a USB stick running ZFS.
> I have created swap file on zfs volume using the md driver.
>
> Swapinfo shows
>
> Device          1K-blocks     Used    Avail Capacity
> /dev/md0          4194304        0  4194304     0%
>
>
> The system has hung twice and all I can find in the log is
>
> Mar 22 03:17:30 server kernel: swap_pager: indefinite wait buffer:
> bufobj: 0, blkno: 927, size: 4096
> Mar 23 09:00:26 server kernel: swap_pager: indefinite wait buffer:
> bufobj: 0, blkno: 55, size: 4096
> Mar 23 22:01:26 server kernel: swap_pager: indefinite wait buffer:
> bufobj: 0, blkno: 49, size: 4096
> Mar 24 04:00:38 server kernel: swap_pager: indefinite wait buffer:
> bufobj: 0, blkno: 60, size: 4096
>

That generally means that your storage is too slow (to handle swap).
See also FAQ:
http://www.freebsd.org/doc/en/books/faq/troubleshoot.html#INDEFINITE-WAIT-BUFFER

> As the swap is on zfs, I assume it is not failing.
>
> Do I need to move swap off of ZFS?
>

IIRC swap on ZFS is generally a bad idea.
Search web for bad stories.

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