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From: envbvs@epb2.lbl.gov (Brian V. Smith)
Newsgroups: comp.sys.dec,comp.unix.ultrix
Subject: Re: How to get best Ultrix TK70 back-up performance over Ethernet?
Message-ID: <3836@helios.ee.lbl.gov>
Date: 19 Sep 89 18:43:00 GMT
References: <11523@watcgl.waterloo.edu>
Sender: usenet@helios.ee.lbl.gov
Reply-To: envbvs@epb2.lbl.gov (Brian V. Smith)
Distribution: comp
Organization: Lawrence Berkeley Laboratory
Lines: 30

In article <11523@watcgl.waterloo.edu>, idallen@watcgl.waterloo.edu
(Ian! D. Allen [CGL]) writes:
 
< Consider a vs3100 and a vs3200 on an Ethernet, both running Ultrix 3.0,
< soon to be Ultrix 3.1 (UWS 2.1).  The vs3200 has the TK70 tape drive.  I
< tried the following to back up 119 Mb from an rz55 on the vs3100 to the
< TK70 on the vs3200:
< 
<     vs3100# rdump 0f vs3200:/dev/rmt0h /dev/rrz1c
< 
<       - estimated 8 HOURS to write 119 Mb to the TK70
< 
<     vs3100# dump 0f - /dev/rrz1c | rsh vs3200 exec dd bs=20k of=/dev/rmt0h
< 
<       - estimated 22 MINUTES to write 119 Mb to the TK70
< 
< Surely there must be a way to get rdump to do better than 8 HOURS for
< 100 Mb?  Enlighten me.  I would have thought rdump and rmt would be
< able to pick the fastest way without my help; I must be very wrong.

The problem is that rdump doesn't use multiple buffer write to the tape,
so the TK50/70 doesn't have a chance at streaming.

dd and tar do use the multiple buffer scheme, so until DEC changes
rdump to do this I would never consider using it.

_____________________________________
Brian V. Smith    (bvsmith@lbl.gov)
Lawrence Berkeley Laboratory
I don't speak for LBL, these non-opinions are all mine.