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Cannot backup data over 12GB on 24x6 autoloader

Tran Phong Vu_2
Occasional Contributor

Cannot backup data over 12GB on 24x6 autoloader

I faced problem that i was using OmniBack II 3.5/Windows NT 4.0 to daily backup data on 24x6 autoloader (each slot used for each day of week).With amount of data over 12GB (but under 24GB),it couldn't proceed on the same slot and required to change another tape.In the Monitor screen of OBII, it appeared msg "mount request ..." or smth like that.Be notice that i've checked the option box "Hardware compress" in the Tape configuration session of OBII.
I tried using NTBackup program, it happened with similar result,i.e cannot backup data over 12GB.
I think i misconfigure smth.Anyone experienced this problem pls give me an advice.
It's urgent, pls help.
Michael Tully
Honored Contributor

Re: Cannot backup data over 12GB on 24x6 autoloader

Have you tried to run this backup without hardware compression? What files are you attempting to backup? If they are already compressed, i.e. say winzip files, then you are not going to get further compression onto your tape. The 12Gb is measured as worst or raw and the 24Gb rating is at best compression.

In regards to the mount request, the backup has not finished and is asking for a second tape. As long as you have a pre-allocated number of tapes in your media pool and in your autoloader, omniback will load the next tape.
Anyone for a Mutiny ?
Leif Halvarsson_2
Honored Contributor

Re: Cannot backup data over 12GB on 24x6 autoloader

24GB compressed data on a DDS3 tape is only an average, the actual compression ratio depends very much on the data. Some cases when you get a poor (or no) compression.
- The files is already compressed.
- Disk compression is used.
- The compression algoritm dont work well on some data (you get a low compression ratio).

In the bottom of the autoloader there is some DIP switches, if I remember correct one of them can be used for switching compression off.
Check this switches, the settings below should work for Windows.

1 on
2 on
3 off
4 on
5 on
6 on
7 on
8 on

Another test you can do is to unload the tape driver, OmniBack dont need this. If this is done your device adress should look like
scsi0:.... instead of Tape0:.... .
Sven Jacobsen
Occasional Advisor

Re: Cannot backup data over 12GB on 24x6 autoloader


just to add some information to Leif??s note:
the 2 important switches on the dip switch are 1 and 2.
1 is for compression on/off
2 is for host intervention
If both are set to on (default) your software can turn the compression mode on and off, which is what is meant by host intervention).

As I said: just for your info!