We used to back up our systems with a scheme that used tee to hand the
output of pax -w to cksum and the tape. After writing all the files we
had one checksum for all the files. We then did a “tape bot” and
cat $tpdev | cksum.
In every case where an error ocurred, the simpler (and faster)
method similar to what Padraig describes would have also caught the
fact that the backup was bad or incomplete.
The cksum method required a fast cpu or a slow tape drive to maintain
a reasonable level of streaming. It also seems to cause Fsys.sym8scsi
failures with certain chipsets.
One other thing we do in our current script is to make certain the last
file written is read back.
Padraig Furlong wrote:
Joseph F. Muscarella wrote:
read the backup from the tape and use pax -v - if data intact
list all the files
Thanks for the reply. How would I automate this as part of my
script? Also, I would want errors only to be reported, not all
This doesn’t necessarily indicate errors within individual files,
Are you using pax -w ‘files to be saved’ | vol -w ‘tape device’
if you are, then the reverse vol -r ‘tape device’ | pax -v will read
and check the data written to the tape. If it is successfull then the
archive is OK
Most tape backup software provides a verify feature to make sure
data written to tape is intact. This is what I am looking for. I
think I asking too much since my data is important and I want
that the backups are valid.
Joseph F. Muscarella