On Thu, 8 Dec 1994 11:22:28 CST Larry Sanders, VM System Maintenance said:
>On Wed, 7 Dec 1994 13:51:33 PST Peter Hadikin (HDIP9235) said:
>>We have an ADSM server running under VM. I am finding that when migrating to
>>tape cartridge we are only writing about 400 meg of data per cartridge before
>>to see much more that 400 meg of data being written to a cartridge.
>
>Is data compression being done by the client workstations?  If so, then I
>think that you should expect to see little or no additional compression from
>IDRC.  On our 3490 drives with standard 3480 cartridges and IDRC, ADSM
>reports from 180 to 200 MB of data on full volumes.  If you are using
>standard length cartridges with 36-track bidirectional recording, 400 MB
>sounds about right.

I have Memorex equivalents of 3490E tape drives and am using the 3490
extended length cartridges with data compression on the clients and am
seeing about 800M per cartridge.  So I'd say 400M is about what you would
expect from standard length cartridges.  You can store more on the tapes
without data compression on the clients if you're willing to pay the
network bandwith though.  In tests I got about 1200-1400M on a 3490
extended cartridge but, we decided to just buy more tapes rather than
pay the extra 30-50% of network traffic during a backup/restore.

---
Keith A. Crabb         Keith AT UH DOT EDU
Keith A. Crabb         Keith AT UH DOT EDU
University of Houston  Operating Systems Specialist +1-713-743-1530