topic Compression in StoreEver Tape Storage

Compression

Steve Friday — Wed, 17 Apr 2002 11:48:31 GMT

Can anybody assist in this matter,

we have an NT4 server sp6a, we are running omniback 4.1

C drive = 1.8G
E drive = 38,8G

Total = 40.6G

We are trying to backup to a DLT VS80 with hardware compression, however it always asks for a second tape?

We do have compression on the E drive so I am guessing that omniback can not compress the files any more than they are already.

Is this correct?

Steve

Re: Compression

CA628575 — Wed, 17 Apr 2002 13:35:07 GMT

Are the 38GB on your E: drive the compressed data size or the uncompressed data size?

If it is the compressed data size, there is the question if the tape drive can achieve the same level of compression than the file system? Since your margin is fairly slim, even a small change in the compression ratio may push you over the edge.

You must also consider that OB has to store some amount of meta data on the tape along with the actual backup data. That can increase your space usage as well.

If it asks you for a second cartridge, how much data does OB write onto the second cartridge (should be visible in usage info for the second cartridge after the backup)?

Re: Compression

BR19682 — Thu, 18 Apr 2002 04:52:11 GMT

Hi there.
Sorry for this question, but what about the
tape ? Large enough ?
We use DLT drives und almost put 80 GB on one tape.
Rgds
Alexander M. Ermes

Re: Compression

Steve Friday — Thu, 18 Apr 2002 06:37:59 GMT

They are 40/80 tapes

Steve

Re: Compression

CA628575 — Thu, 18 Apr 2002 11:21:19 GMT

There is only one tape length for DLT drives (referred to as 40/80 - or DLT IV). This means they havea a capacity of 40 GB uncompressed, 80 GB compressed (assuming an average compression of 2:1).

Assuming that the 38GB is compressed capacity, it will probably be not compressible anymore, meaning you will pretty much use the whole cartridge (or slightly more).