ZFS - Unable to offline drive in raidz1 based pool

[James R. Van Artsdalen]

Kurt Touet wrote:
> I wonder then, with the storage array reporting itself as healthy, how
> did it know that one drive had desynced data, and why wouldn't that
> have shown up as an error like DEGRADED?

The uberblock on each ZFS disk contains a txtag, in effect a revision
number.  When a pool is imported and one drive's txtag is older than the
others then that drive needs resilvering.