ADSM-L

Re: Slow backups

1994-08-17 10:47:38
Subject: Re: Slow backups
From: "Ross Patterson" <Ross_Patterson AT Sterling DOT Com>
To: ADSM-L%MARIST.BITNET AT uga.cc.uga DOT edu
Date: Wed, 17 Aug 94 10:47:38 EDT
>> We have ADSM running on our LAN server. It is an IBM model 95. We
>> are using TCP/IP for the communication on a 4Mb T/R. It is taking
>> 10.5 to 12 hours to backup 1.3Gb of data. Is this normal?
>
>If this is the first backup of this machine, it's not too out of
>line. You don't say what tape device you're using, but most of
>the 8mm variety won't exceed 400-500K/sec no matter how fast your
>network connection is. The subsequent backups will be only
>incremental (changed files), so it won't take nearly that long.

Also don't forget the bits-to-bytes conversion factor.  1.3 gigabytes
of data in 10.5 hours is 37 kilobytes per second, ignoring "minor"
issues like packet-framing, protocol overhead, and other users on the
ring.  That isn't stellar performance, but it approaches 10% of the
full-bore data rate on a 4 megabit/second token ring (524 kilobytes/second
by the same computation).  By coincidence, this is roughly the same maximum
David quotes for 8mm tape drives.

Ross Patterson
Sterling Software, Inc.
VM Software Division
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