Making amdump conditional on amcheck doesn't make sense.  In
particular, you probably want amdump to run and dump to holding disk
if there is no tape, and if even 1 host is up you probaly want that
host backed up.  I would expect that on configs with 100 clients that
a typical night involves a client timing out.  As long as it's a
different client every night, that's no problem - if you run amdump
anyway.

amverify is useful to see that bits can be read back from the tape.
It isn't a full restore test (for that, pick a random employee and
have then pick an important file, and go get that and present it to
them for validation), but it mostly checks that your tape drive can
read bits back, especially if you gzip.  The dump files are
uncompressed and run through restore to verify format.

I had a tape drive or scsi bus fail such that most of bits were right
but there was a lot of corruption.  one could read files back, and
most of them had gzip failures.  We replaced the tape drive, and the
problem has not recurred.  But, we run amverify once a week (on the
weekend, using hte tape from Friday night's dump) to verify that we
aren't having a similar problem.

So, you really should do a test restore once a week.  But if you, like
most humans, don't, then a weekly amverify is a good idea.

-- 
        Greg Troxel <gdt AT ir.bbn DOT com>