Slow dump/restore of ra90s on DECsystem 5810 (Ultrix 4.0)?

[Michel Fingerhut]

Having had disk problems on ra90s, we had one replaced.  So as to copy the
file systems from the old one to the new one, we ran a dump of each fs in
the old one piped into a restore on the corresponding fs on the new one.
This was run in single user mode, and single jobs: nothing done in parallel.

It took an incredible long time to perform: for a 500 Meg partition -- over
2.5 hours.

Does anyone have a clue as to why?  Disk performance, controler management of
accesses to different drives, pipe problem or what?

Thanks for any help,
Michael Fingerhut