I bought a Quantum VS160 DLT drive a couple weeks ago to backup my
network. It's in a Linux system (Gentoo distro, heavily optimized 2.6
kernel and system software) with a 2.8GHz P4, 1GB RAM, and a pair of
120GB 7200 RPM IDE disks (on separate controllers). 

I think the tape drive is so fast that Amanda (or dump or tar) can't
make it stream. The disks are just too slow to write to and read from at
the same time. 

I got dump to work using Amanda's trick of dumping to disk, then copying
to tape -- but I used dd with 1MB buffers, turned the tape drive's
hardware compression off, and made sure there was no other disk
activity. Run that way, the computer can keep up with the tape with a
70% or 80% duty cycle on the disk activity LED. With compression on, the
duty cycle goes much higher, and 3 or 4 times during the 47GB transfer,
the tape drive ran out of data.

Restore, of course, is hopeless, streaming-wise.

I know I could do amdumps and then amflushes at 3:00 AM, but if I could
get Amanda to wait for all the dumps to come in before writing to tape,
I think things would be OK. I wouldn't mind dedicating an IDE drive as
the holdingdisk, but I'd hate to have to buy a 60GB SCSI for that.

Is there a way to get Amanda to schedule this way? Does using mt to set
a tape's blocksize affect buffersizes in taper?

-- 
Glenn English <ghe AT slsware DOT com>