On Wed, 2004-06-02 at 10:59, Jon LaBadie wrote:

> I doubt there is any tapedrive that is "too fast" for your
> disk drives.

I thought so too. But when dump is running from one disk to the other,
it reports speeds about 20% higher (~10MB/s) than it does when running
from disk to tape (~8MB/s). I can get dump to stream by specifying a 1MB
blocksize and making sure there's no other disk activity.

The problem seems to be with writing and reading at the same time. The
disks (IDE 7200 RPM Seagate Barracudas) don't seem to be fast enough to
do the seeks and additional IO -- the access LED is on continuously, and
the tape is stopping, rewinding, and writing very frequently. Just with
the VS160 -- there's never been a problem with the DAT drives I've used
in the past.

> Are you sure your configuration is using amanda's holding disk
> feature.  

Absolutely. amdump creates a directory in /amandadisk, and dumps from
the net are stored there. If there's a tape in the drive, they are moved
to tape. Otherwise I can get them on tape later, with amflush.

> From the holding disk, amanda uses the equivalent of dd to send
> a complete dump from disk to tape.  Only if the holding disk is
> not being used for the dumps might the speed of tar/dump be a
> factor.

I started using the tar/dump/dd commands directly (for troubleshooting)
only after a couple days trying to get Amanda to stream the tape. 

If I've misinterpreted or misconfigured something, I'd certainly like to
hear about it.

-- 
Glenn English <ghe AT slsware DOT com>