I use bpmedialist -m <tape number> to get all tape information - This will tell you the compressed amount of data that is currently on a specific tape.
For total capacity you need to know what kind of tapes you are using as well as drives. I have written up a summary of drive speeds etc - THis might help you to determine your actual tape capacity.
Tape Drives
• DDS2 rated as being able to write 1.6GB/hour native and 3.2GB/hour compressed. (4/8)
• DDS3 3.5GB/7GB per hour (12/24)
• DDS4 10GB/20GB per hour (20/40)
• DLT4000 5GB/10GB per hour (20/40)
• DLT7000 18GB/36GB per hour (35/70)
• DLT8000 21GB/42GB per hour (40/80)
• SDLT 38GB/76GB per hour(40/80)
• LTO 53GB/106GB per hour (100/200)
• LTO (Gen2) 100GB/200GB per hour (200/400)
To calculate what you expect to be the data rate for backups, take the following calculation:
Tape Drive MB/Sec x(Compression factor – Usually 1.5) x 3600 / 1024 to give you your rate per hour in GigaBytes. e.g. A DLT7000 rated at 5MB/sec is:
5MB/sec x 1.5 x 3600 / 1024 = 26.4GB/hr. A LTO will be 79GB/hr.
The numbers in brackets are the capacity ratings of the tapes i.e. 100/200 = 100GB regular and 200GB compressed.
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