Swap on ZFS / swap_pager: indefinite wait buffer

[bsalinux at gmail.com]

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

As the swap is on zfs, I assume it is not failing.

Do I need to move swap off of ZFS?

Thanks