Tape Capacities

[Paul Murray_1]

Hello All,

Can anyone tell me of a command to establish the capacity of a tape/drive ?

I've tried using cstm, and this seems to work fine on DDS (once a tape is loaded), but no values appear on DLT drives.

Any ideas ??

TIA,

Paul.

[harry d brown jr · Accepted solution]

Capacity of dlt tape drives is quite simple. If you have a dlt 40, it means it can hold 20gb of compressed data, at a 2:1 compression ratio. A dlt70 can likewise store 35gb of compressed data, and a dlt80 can store 40gb. But a thing to remember is that it also depends upon your media. If you use a 20gb dlt tape in a dlt80, it will not store 40gb.

http://www.hp.com/cposupport/information_storage/support_doc/lpg50550.html

http://www.hp.com/cposupport/information_storage/support_doc/lpg75090.html


live free or die
harry

[harry d brown jr]

Heres another good source:

http://www.unylogix.com/data_storage/tapes.html

live free or die
harry

[Bill Hassell]

And to add to Harry's comments, the tape drive model determines the maximum capacity. A lower numbered tape drive can't record onto a higher numbered tape, while the reserse is OK. Also, compression is either on or off (via device file option bits) and the ratio of cpmpression is always dependent on the actual data.

Therefore, highly random data or data which is already compressed will not compress further and the capacity will be native (ie, DLT80 = 40Gb). It's best to plan for native capacity rather than rely on thwe 2:1 ratio until you know the nature of the data.