Hello,

last week I posted a message concerning performance
on our new IBM 3494 robot with IBM3590 SCSI units
under AIX attached to SP2 with Wide SCSI I/O controller.

I was comparing my figures of around 3 MB/sec using
ADSM archive/restore from local disk to attached 3590 tape
to the published rates of 9 MB/s and even 11 MB/s using
compression 3:1.

I was pointing at the difference of these numbers and was asking
if someone else has seen better figures.

In the meantime we did more measurements with the following results:

reading from (local) disk is a bottle neck which cuts performance at 3 MB/s
  (This applies to ADSM and other programs like dd)
reading from (local) disk with memset comes up to 7 MB/s (100 MB, 64 K blocks)
writing from memory to 3590 tape comes up to 7.8 MB/s (200 MB data, 128 K 
blocks)
you can improve this to 8.7 MB/s setting compression off on the device
with compression on and compactable data 2:1 you can get 11.7 MB/s (200 MB 
data, 256 K blocks)
ADSM maximum rate I got was 5.6 MB/s for transfer from tape to tape

These rates show that SCSI connection and IBM3590 can work at the
claimed performance.

There is however a restriction that
memory to tape is needed to get max numbers,
and hardware compaction=on with uncompactable data
  downgrades the performance.

By the way a last question:

The time needed to close the tape after writing one file
seems to depend from the filesize
(from 8 sec for 100 MB to 13.5 sec for 200 MB).
Why ??

Thank you for listening.

------------------------------------------------------------
Matthias Feyerabend            phone:    (49) 6159 71-2519
Matthias Feyerabend            phone:    (49) 6159 71-2519
GSI, Darmstadt                 internet: M.Feyerabend AT gsi DOT de