I have just gone through an interesting problem with a DAT drive that I
thought I would share (like you want to share my problems.)

While doing a disaster recovery test at a hotsite we were unable to
restore data written on one of my drives. (The backup is written to 3
drives.) I was receiving an error message that basically stated that the
DAT couldn't be read, something like UNIT FAILURE. This can indicate a
dirty tape drive a bad tape or any number of things. I cleaned the
drives to no avail. I figured it was a bad tape. Since this was a
secondary system I said, "We'll test it next time."

Well next time came and the same problem occurred. Now I call the
Response Center. They said that firmware revs should not matter. They
told me to look at the compression. On all three of my drives the DCE is
on (1). I disabled the compression on the drive in question and the
hotsite can read the tape. Turning off compression may solve the hotsite
problem but it will also mean that the hardware compression feature is
unavailable if I need it.

My question is, "Why is this drive different from all other drives?" The
compression being on didn't matter with the other drives. Is this
another one of those alignment problems? Is it possible to be
misarranged only at high compression? Is this a hardware compression vs.
software compression issue?
I am using compression in the store job (ROADRUNNER.)

Any ideas would be appreciated.

My opinion are my own, no one else wants them.