rewinding a disk drive takes too long

[Peter Jeremy]

On Sat, Jan 17, 2004 at 09:55:53PM +0000, Randy Bush wrote:
>dumping to a remote disk a la
>    /sbin/rdump 0Luaf foo.bar:/backup/usr /dev/ad0s3g
...
>  DUMP: 99.54% done, finished in 0:01
>  DUMP: 101.28% done, finished in 0:-3   <<<<<<<<<========
>  DUMP: DUMP: 7473583 tape blocks on 1 volume
>
>that seems a long time to rewind a disk file :-)
>
>and it paused at 0:01 for at least five minutes

[r]dump(8) provides a status report every 5 minutes.  The '% done'
field is based on the initial estimate of how much data needs to be
written and the time field is an estimate of how until it reaches 100%
done based on the rate to date.  If you're dumping an active
filesystem, it's possible that the initial size was an under-estimate
(if you look back, you'll probably find that it was about 3% less than
the 7473583 block actually dumped).  At the time of the last report,
it had dumped 101.28% of the estimated volume and so estimated that
it reached 100% 3 minutes previously.

Peter