From: Mike Knight, DCS-East, (314)234-5096, KNIGHTM at ISSCVM
Inet:                                       KNIGHTM AT VNET.IBM DOT COM
Subject: DLT Tape opinions

On 6 Feb 1996 17:27:10 EST, Paul Zarnowski wrote:

> I am somewhat concerned that ADSM will not be able to drive the DLT drives
> at their rated speed.  At some point, I think database updates may become
> the limiting factor.  We are using regular fast scsi-2 drives for our db
> (barracudas from seagate).  We have not been able to drive our 8mm drives
> at their rated performance, and I am not sure what the reason for this is.

We have similar experiences with an RS/6000 580 not being able to keep up with
8mm drives.  We have not studied it, but believe it is mostly on small to
medium files with more database work relative to the file data.  We see some
delays from the disks (IBM 4.5GB fast/wide) and very heavy CPU usage,
especially when several sessions and processes are running.  We are purchasing
an upgrade to a 590 in hopes it will help.

The delays are compounded by the 8mm drive having to backspace when the CPU
can't pump out data fast enough.  I have heard this is less of a problem with
DLT or 3590, but have nothing to verify this.
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We also are contemplating switching from 8mm to DLT.  If Exabyte had
their Mammoth drives out it would be equivalent to DLT in speed and capacity.
Who knows when they will be available and when ADSM support will be certified.
We can't wait on Exabyte forever.

Our other concern is with that we will buy DLT libraries and ADSM will announce
support for better libraries a few days later.  Are there other brands and
models in the ADSM pipeline?  I am personally worried on drive shortages if we
get the big 2.5TB Odetics libraries with only three drives each.

         Mike (Not ADSM Support) Knight