"Dean Pearson" wrote in message
news:1110321796.779597.208780@o13g2000cwo.googlegr oups.com...
>I have a DLT 7000 with brand new Sony DLT IV tapes and when I backup
> about 60G from several directories using tar on FreeBSD
> 5.2.1-RELEASE-p13 I can only ever get 45G out of the tape before it
> falls over with:
>
> Total bytes written: 48194365440 (45GB, 3.6MB/s)
> /usr/bin/tar: /dev/sa0: Wrote only 0 of 10240 bytes
> /usr/bin/tar: Error is not recoverable: exiting now
>
> Prior to the tar command I collate a file full of sockets and FIFO
> files which I pass to tar in a exclude-from argument, so I would not
> imagine it to be a file to cause the premature end.
>
> I have tried several SCSI cables and several SCSI cards, I have tried
> many tapes and still I seem to hit this limit. Does anyone have any
> ideas?
>
> Kind Regards,
> Dean

You get what you paid for. A DLT-7000 is 35GB native, minus some tar and
tape handling overhead you can expect about 32GB or so available. With 45GB
on tape you are getting 1.4:1 compression out of the drive. Nothing wrong
with your system.

Rob

1.4:1 is about typical for a full system backup. The 2:1 marketing
figure applies to text files (sometimes.) With some files you can get
higher compression factors (rarely), with uncompressible files (e.g.
JPEG, MPEG or .gz) you'll even get less than 1:1 - in which case it
makes sense to turn compression off.

Ralf-Peter