Snaphot stability issues on 6.3

[Michael R. Wayne]

One of our servers, running a bunch of jails, has issues when doing
nightly dumps only if snapshots are enabled.  This box was running
5.X and has been upgraded over time to 6.3.  When running 5.X, we
attempted to use snapshots on dump (-L) which resulted in almost
nightly system hangs during the dump.

We ran 6.X for months with no stability issues, backing up nightly
w/o snapshots.  Took the system down to single user mode, did
foreground fsck, enabled -L on dumps and the machine "kinda" hangs
twice a week (main host seems OK but jails stop responding and can
not be properly stopped), requiring a reset.  Removing the snapshots
restores system stability.  Foreground fsck finds nothing unusual,
just what I would expect when doing a reset on a live filesystem.

I suspect that there is some corrupt filesystem residue from 5.X
since we have no similar issues on 6.x clean installs.  Is there
something better than just fsck to attempt to resolve these issues?

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