Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!uunet!mcsun!unido!mikros!mwtech!martin
From: martin@mwtech.UUCP (Martin Weitzel)
Newsgroups: comp.unix.i386
Subject: Sudden performance drop of streamer tape
Message-ID: <793@mwtech.UUCP>
Date: 9 Jun 90 01:56:43 GMT
Reply-To: martin@mwtech.UUCP (Martin Weitzel)
Organization: MIKROS Systemware, Darmstadt/W-Germany
Lines: 26

Just half an hour ago the following happened with my streamer
(System Info: ARCHIVE FT 60 / 80386 / ISC 386/ix Rel 2.0.2):
When backing up a file system that would usually be copied at full
streaming spead (~80 KB/sec) the performance was ABSOLUTELY DOWN!
There were tape stops approximately every 32 KB (which is the block
size the driver internally uses, for as much as I know).

As I knew that performance usually was *much* better, I shutdown the
system, rebooted, and - voila - speed was back again: The same file
system could be copied as fast as ever. Nothing else was changed!

Any ideas? As further information I should tell that I had several
times the tape operation aborted (with SIG_INT from the keyboard)
before the strange effects begun.

Some other idea is that memory might have become too fragmented to
allocate suitable buffers. (May this be a problem at all? How can I
check for this if the performance drop should occur once again?
Could this be cured without rebooting? Before rebooting I changed
to single user mode and back, but that didn't help.)

Though bringing my system down and rebooting is not much of a problem
in the environment where I work, I would be glad if someone could
enlighten me about what may have happened.
-- 
Martin Weitzel, email: martin@mwtech.UUCP, voice: 49-(0)6151-6 56 83