Path: utzoo!mnetor!uunet!husc6!bloom-beacon!gatech!purdue!umd5!umbc3!tron!carson
From: carson@tron.UUCP (Dana Carson)
Newsgroups: comp.unix.wizards
Subject: Re: DEC TK50 tape drive performance w/4.3BSD
Message-ID: <184@tron.UUCP>
Date: 23 Mar 88 17:50:55 GMT
References: <160@polygon.UUCP>
Organization: Westinghouse D&EC, Baltimore, MD
Lines: 19
Keywords: DEC,TK50,tape,dump,unix
Summary: Might be streaming problem

In article <160@polygon.UUCP>, mehr@polygon.UUCP (Mark Ehr) writes:
> I have a DEC MicroVax II, which (unfortunately) has the TK50 cartridge tape
> drive as its' only means for backup.  I am having *terrible* performance
> with dump (I have 4.3 BSD, by the way);  as an example, I can generally
> only get around 35 megabytes on the tape;  DEC's specifications say that it
> is a 90+ megabyte capacity cartridge.
> Mark Ehr @ Polygon Network, Inc. (uunet!polygon!mehr)

I know that under Ultrix 1.2 vs. 2.0 there was a big improvement by
going to more buffers for streaming.  The problem is that if data
doesn't come in fast enough the tape controller will pad with 0s to keep
the tape streaming. It will do this for a while and then give up and
backup to where real data left off. If you are just slow enough that you send 
the next data buffer before it gives up you use up a lot of tape with
padding.

--
Dana Carson
Westinghouse