In the Networker nwadmin gui, there is a configuration under Media, Devices, where you can set the volume capacity.
I set the capacity to 40GB on all the devices, then labeled a new DLT Compactape IV. I then checked the volumes with a mminfo -m and there it changed the default capacity to 40GB. So from now on when I label a new volume I am set.
There is another way to change the capacity through the command line: nsrjb -L -f /dev/rmt/*hbn -c 40gb -S *
(This will work for each volume, but doesn't change the device configuration.)
Other suggestions were to use /dev/rmt/*cbn.
AND
The hardware compression that is used on tape devices is highly data-dependent. Some data compress better than others.. I usually get around 27Gb on a DLT4000.. BTW, I usually use the /dev/rmt/*ubn device; you might be able to squeeze a few more gigabytes from your tapes by using the ubn versus hbn..
I would still like to find some documentation for the cb, ub, and hb in the /dev/rmt/***n.
Thanks to:
Ted Marigomen
Brad Young
Original problem:
> Sun Managers,
>
> I am using an ETL4000 jukebox with 4-devices (tz88 or 89), backing up to a DLT Compactape IV. The backups work great, but I can only squeeze 20 GB of compressed data on each cassette. I know the cassettes are rated up to 40 GB with compression, and I am sending to /dev/rmt/*hbn device, which tells me I am only using hardware compression.
>
> The command mminfo -m tells me the jukebox is configured at only 10 GB. There is nothing in SunSolve or the 4000's documentation that could tell me how to change the devices capacity for a Compactape IV.
>
> I would really like to get 40 GB on the cassette, instead of only 20 GB.
>
> "Out Standing" in Omaha
>
> And of course...Thanks in advance!
> Steve
> mcneill@top.net