LTO3 Total Capacity differences between Quantum and IBM drives

[Mark_Walker]

We recently had a Dell 124T autoloader with the half-height Quantum drive replaced with a 124T containing the full-height IBM drive due to hard write errors.

All tapes written by the Quantum show Total Capacity of 400.5 GB in properties.

All tapes written by the IBM show Total Capacity of 372.5 GB in properties.

Dell was no help.

Thoughts about this difference?

All the tapes in use are LTO3 400/800.  We run Backup Exec 12 SP2.

[Larry_Fine]

The capacity is just a number reported by the drive.  Apparently the vendors report slightly different numbers.  It may have a slight impact in the apparent (but not the real) compression ratio.  BE doesn't actually use that number as a limit, it is mostly a cosmetic thing to give users a rough idea.

[Mark_Walker]

While I understand your explanation, I'd have to see some evidence from Symantec or IBM.  Everywhere I look, including the manual for the device, IBM says, "Native storage capacity of 400 GB per cartridge (800 GB at 2:1 compression)" for their LTO3 drive.

[Larry_Fine]

If you take a media showing 400 GB capacity, move it to retired, delete it from BE, then inventory it in an IBM drive, what does the capacity show?

[Mark_Walker]

The display changes from:

total capacity: 400.5 GB
used capacity: 400.5 GB of 400.5 GB

to:

total capacity: 372.5 GB
used capacity: 64.0 KB of 372.5 GB

[Larry_Fine]

I think that demonstrates that the different brands of drives report the same media differently.  Solution? Or am I not understanding your question?