If you are running a-sis with 7.2.3 or 7.2.3, there are a few bugs that can cause the filer to panic and mark that volume offline forcing a wafl_check on the containing aggregate. Not only that, but we had to netboot a developer release and had extensive outages.
We have been told that 7.2.4 had fixed these bugs, but if you have run asis on an old version, the bug may be there dormant.
I believe these were the bugs that were identified in our incident report.
bug 256799 Bug 266312 Bug 276084 bug 266312 bug 251673
The bug hit our primary storage, and it also his the VSM volumes on our DR filer, and it would is in the ACL/directory of the backup tapes as well.