== An Amanda gotcha with dumps to disk

One of the configurations that [[Amanda http://www.amanda.org/]] supports
these days is dumping to disk instead of to tape. The leading way to do
this is to use your disk space as virtual tapes, using the 'file' output
driver (per [[here http://www.amanda.org/docs/howto-filedriver.html]]).

When you do this, it is vital to remember that ~~to Amanda, these are
tapes~~. Very fast tapes, but tapes. And they have all of the limitations
of tape. Such as that only one thing can be written to them at once.

So if you do not set up a holding disk in addition to your disk space
for the 'tapes' (because why would you need a holding disk when you're
dumping to disk anyways), [[Amanda]] will behave just like it would with
a real tape: it will serialize all your backups, because they have to go
to directly to tape.

(It is surprisingly hard to notice this, because the daily Amanda reports
do not mention that they are dumping directly to tape and does not have
the start time of the various dumps, which would have let us see this
clearly. However, [[amstatus http://www.amanda.org/docs/amstatus.8.html]]
will tell you that only one dumper was ever used, which is a dead
giveaway, and you can run [[amstatus]] even after amdump finishes.)