Internal compression StorageWorks DAT 40i?

[Johan Orö]

What is the level of compatibility between different tape drives and external compression SW when the internal compression is turned on?

Is it e.g. possible to read a DAT 40i compressed tape from a linux machine equipped with a non compression tape drive using the tar "z-option"?

[Dave Dewar]

Hi,

Internal Compression on tape drives is exactly that, its INTERNAL.

The bit stream is compressed before being actually written down to tape and then the process is reversed during read back. The data going into and out of the host interface of the tape drive is uncompressed.

Hence, if you put a tape from a DAT drive that had compression turned on, into a DAT drive that does not have compression at all (this must be a very old drive since I think we only shipped a DDS1 product without compression hardware) you will not be able to read it no matter what compression software you use.

Cheers,

Dave Dewar