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From: ridder@elvira.enet.dec.com (Hans Ridder)
Newsgroups: comp.sys.amiga.hardware
Subject: Re: Problems with V6.6 A2091 ROMs
Message-ID: <3411@shodha.enet.dec.com>
Date: 19 Jun 91 23:41:03 GMT
References: <3325@shodha.enet.dec.com>
Sender: news@shodha.enet.dec.com
Organization: Digital Equipment Corporation, Customer Support Center
Lines: 42

In article <3325@shodha.enet.dec.com> ridder@elvira.enet.dec.com (Hans Ridder) writes:
>I got the new V6.6 A2091 ROMs a few weeks ago, and finally had a chance
>to try doing a backup to tape.  I don't know what I could be doing
>wrong, but the backup performance is worse than ever.
>
>Here's the whole story.  I have a 3 meg. A2000HD running 1.3, a 3M
>MCD-40 tape drive, and am using BTNtape and tar for backups.

After all the noise about the reselect problems on the A2091, I would
have thought I'd get more response to my posting....  (Maybe everyone
knew I'm nuts, huh?)

For the record, the V6.6 A2091 roms are just fine.  They reselected
their way through about a dozen backups without a hitch.  The problem
was (mostly) pilot error.

For the benefit of other 3M MCD-40 owners and BTNtape users, when I
formatted some new tapes to do the backups on, I used the 2.0 version of
BTNtape.  It suggestes a format command which specifies an interleave of
two, while the 1.0 version has a file specifying an interleave of three.
I didn't notice the difference.  The lower interleave factor means that
the average data rate is higher, and the disk couldn't keep up with the
tape causing the tape to stop.

After some messing around with the tapes interleaved at two, I found
that by upping the handler priority to 11 (higher than the disk file
system) and upping the blocking factor ("NB" parameter) to 4, I can
backup 37 meg of data in 34 minutes.  (It used to take about 30 minutes
for 10 meg.)  The net result is a faster backup than ever!

Increasing the blocking factor to 10 reduces the time to 32 minutes (and
only about 160 Kbytes of buffer space is used :-)) Just for reference,
with the increased priority and block size, the tapes with an interleave
of three give a backup time of 49 minutes.

>-hans

-hans (again)
------------------------------------------------------------------------
  Hans-Gabriel Ridder			Digital Equipment Corporation
  ridder@elvira.enet.dec.com		Customer Support Center
  ...decwrl!elvira.enet!ridder		Colorado Springs, CO