Consider following scenario:
1. you backup say 40 GB
2. next day you backup 40 GB of which 35 GB updated - 35 GB from step 1
expire.
3. perform step 2 for four days.

The result you have 40 + 4x 40 GB = 200 GB written on tape. Tape reached
the end and becomes "Full". At the same time you had 4x 35 GB = 140 GB
expired. Thus you tape holds 200 - 140 = 60 GB (30%) real-data. The rest
is gaps. Reclamation precess (which is hard, close to impossible, to do on
single drive) can help.

Zlatko Krastev
IT Consultant






Sudheer Kumar <sudheer AT COSMOS.DCMDS.CO DOT IN>
Sent by: "ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>
26.11.2002 14:22
Please respond to "ADSM: Dist Stor Manager"


        To:     ADSM-L AT VM.MARIST DOT EDU
        cc:
        Subject:        tape become full in 21 percent.


Hi

I am using LTO 3580 tape drive. but my tape capacity is 100/200GB but
never got more than 31% utilization. When it reaches 25 to 31percent it
become Full.Can anybody tell me what could be the reason.

Regards

Sudhir