Ultrium 3000 LTO5 - LTFS Hardware Compression

[Werft]

Hello,

I'm unsure about the hardware compression regarding LTO5 tapes.
It would be great if someone could confirm the following:

Currently I use an internal HP LTO5 Tape Drive (Ultrium 3000) with HP LTO5 tapes on Mac OS X 10.9.
An ATTO H644 SAS controller is handling the data.

HP StoreOpen is able to format the drives and mount file-systems.
I'm right now doing read/write tests and im able to get 130MB throughput.

Everything is working good but I was confused when I saw that i could only use 1.5TB - like the hw-compression was set to off. I double-checked - its not disabled via the preferences.

So does LTFS only support uncompressed Sizes (1.5 instead of 3TB)?

I can't check with another tape right now so I'm wondering if my tapes the issue here or did I miss some information?

Thanks a lot for any help

[roy_augustine]

The drive's ability to compress the data depends on the type of data we are writing. If the data is already compressed (zip files, mpeg videos, JPG images etc) the drive cannot compress the data further.

If the data is not compressed (text files, bmp images etc) the drive will be ble to compress it before writing to tape.

When you format a tape in LTFS you can chose to disable/enable compression for that particular tape. By default data compression is enabled when you format the tape in LTFS.

So when using StoreOpen, the capacity of a LTO-5 tape is 1.5TB if the data is already compressed. If it is compressible data the capacity will be 3TB (assuming the data is compressible 2:1)