I have Amanda configured to do all its backups (local and net) to disk.
I set the "reserved" parameter to 0 -- that will make it do complete
backups, right? (As opposed to degraded mode)

And if I run amflush I'll have complete backups on tape of everything in
the disklist, right?

<long story>

A while back, I bought a Quantum VS160 DLT tape drive and found the
amanda backup configuration I'd been using for years (to DDS) wouldn't
stream it.

After much email traffic and hardware futzing, I've come to the
conclusion that it is not possible for my system (linux 2.6, 2.8GHx P4,
2GB RAM) to stream data to that tape drive from one part of a disk (IDE
or SCSI) while writing to another part. But just reading from a
contiguous file on a holdingdisk that isn't doing *anything* else works
fine. 

I think the bare disk drives may be fast enough, but by the time the
drivers and OS get through buffering data and moving it around, the tape
has emptied its I/O buffer and stopped.

The seemingly working configuration:

The holdingdisk is a dedicated 7200 rpm 120GB IDE on its own controller
in a PCI slot. DMA on, drive is a master, 80 conductor cable.

Amanda's configuration puts all the filesystems on a single spindle on
separate spindles and uses gtar as the archiving program (Linux 2.6's
dump kept reporting errors -- maybe because the server is gentoo, and
the clients are RH and debian).

Amdump runs every night, and the reports look reasonable.

Every once in a while, a shell script runs that checks to see how much
data is waiting on the holdingdisk. If it's a significant fraction of
the tape amflush moves the backups to tape, and amverifyrun verifies the
tape.

This seems to be working. Amflush streams the tape (except between tape
files); the tapes verify; files are on the tape; and I can get to them
with amrecover. But just to be sure, do you people think this is a
reasonable solution?

</long story>

Thanks to everyone for your help. This has been quite an education.

-- 
Glenn English <ghe AT slsware DOT com>