LTO capacity

[CA1265179]

Why does a 400G LTO only hold 260G?

[Uwe Zessin]

David,
it would be helpful if you mentioned actual product names / numbers of the tape drive and the media.

Tape drive vendors often give two values: the native capacity of the media and a value assuming a compression ratio of 1:2. Of course, that only works if the data on the disk is compressable. If you have a disk full of JPEGs or ZIP files, you will not reach the higher value, because the data is already compressed.

Trying to compress data that is already compressed results in _more_data.

[Curtis Ballard]

A 400G LTO sounds like an Ultrium 2 HP LTO 460 drive. That drive has a native capacity of 230G so 260G is not unusual if you have a lot of files that can't compress. I have a huge data set of MP3 files I made for testing backups and with that set I get just about the rated capacity. My capacity is better than 2:1 when I back up my HP-UX systems that are used for hosting text records.