🚀 go-pugleaf

We are using a Lago datawheel with two exabyte drives.
After a drive failure, one of these has been replaced with
a drive supplied by Lago Systems described on the box as
a 'DRIVE ASM,8500C'.
I believe this performs hardware compression.
Certainly, if I write to it I cannot read it on the older drive.

Question (1) is : how can the hardware compression be turned off ?

It is connected to a scsi controller in an IBM RS/6000 running
AIX 3.2.5.
The drive is configured as 'Other SCSI Tape Drive'.
IBM engineers have suggested setting the DENSITY setting #1 to
15 or 21 via the software interface provided. Neither had the
required effect.

IBM documentation implies that IBM tape drives support a compression=no
attribute but this is not available for 'Other SCSI' tape drives.

I thought that the compression drive would be able to
read all tapes that had been written on the older drive.
But I find that of the 15 tapes I've tried, 3 can't be read.
We write a header file on each tape using :
dd of=/dev/rmt0.1 bs=1k con=sync
LABEL
Ctrl/d
The failed reads produce :

dd if=/dev/rmt0.1 bs=1k
dd: 0+0 records in.
dd: 0+0 records out.

or :

tctl -f /dev/rmt0.1 fsf 1
/dev/rmt0.1 fsf 1 The process failed.: There is an input or output error.

Question (2) is : does anyone have any idea how we can read these
tapes on an 8500C drive ? This is particularly important as we are
about to replace the 'standard' 8500 drive.

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 Steven Bridge     Systems Group, Information Systems Division
                         University College London