ZFS inresponsive.

[Pawel Jakub Dawidek]

On Sun, Oct 31, 2010 at 01:20:16PM -0500, James R. Van Artsdalen wrote:
> Thomas Zander wrote:
> > Same here, same setup. ZFS, GELI, USB.
> 
> It is not a good idea to use USB disks with ZFS.  It can cause pool loss.
> 
> Many (most?) USB enclosures use USB<->SATA chips that discard the
> SYNC/FLUSH command to the disk.  As a result this opens a window of time
> where disk writes might be reordered in a way that cause the ZFS
> structures to become corrupted.  There's no problem in normal operation
> but there may be a failure if there is a power loss.
> 
> The log entries in Fabian's note look like a USB SYNC/FLASH failure to
> me - that USB enclosure should not be used with ZFS.
> 
> At one time there was talk of "deferred reallocation" in ZFS which would
> deal with broken USB enclosures but I don't know if Sun ever got around
> to this.

Yes, it is implemented in new ZFS. Blocks are not reused for next three
transaction groups and one can import a pool by falling back to the last
working transaction group if the most recent one is corrupted.

-- 
Pawel Jakub Dawidek                       http://www.wheelsystems.com
pjd at FreeBSD.org                           http://www.FreeBSD.org
FreeBSD committer                         Am I Evil? Yes, I Am!
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