anders@perdix.lu.se (Anders Ardo ) (06/26/87)
I have some trouble getting performance out of a Megatape backup
magtape. I have a uVAX running Ultrix 1.1. The Megatape is driven by
the ts11 driver.
Using only the dump command it takes ~ 2.5 hours to fill one tape with
340 MB of data. The tape should nominally hold 500MB. I am told that
the ts11 driver uses 8k blocks which should give this amount of tape
utilization.
If I could increase the blocksize to 32768 (maximum for ts11) the tape
utilization would increase to 438 MB and the time to write the tape
should go dowm.
I tried to do this using the method suggested here earlier with the
following command:
dump 0nf ... | dd obs=32768 conv=block of=/dev/rmt9
This method works fine with the TK50 drive on the same uVAX giving
speed ups of 2-4. BUT for the Megatape - ts11 I actually get a
slowdown from 2.5 hours to 11.5 hours? WHY??
Can I do something else to achive this blocking of 32768 for The
Megatape or are theer anything else I can do to speed up backups?
I have also heard rumors about backup units based on videotapes with
capacities of 1 to 2 GigaBytes. Anyone have some more information or
even experience with these kinds of backup units?
Thanks for any hints or suggestions.
Anders
Anders Ardo Tel: int+46 46 107522
Dept. of Computer Engineering Telex: 33533 LUNIVER S
University of Lund
P.O. Box 118 UUCP: anders@perdix.lu.se
S-221 00 Lund, Sweden BITNET: ddtnet@seldc51