From owner-freebsd-stable  Tue Jan 22  1:38: 6 2002
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Date: Tue, 22 Jan 2002 14:34:47 +0500
From: Sergey Gershtein <sg@ur.ru>
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Organization: Ural Relcom Ltd
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To: freebsd-stable@FreeBSD.ORG
Subject: Strange lock-ups during backup over nfs after adding 1024M RAM
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Hi!

Our server runs FreeBSD 4.4-STABLE.  Until recently everything was
ok, but when we increased the amount of RAM from 1024Mb to 2048Mb
strange lock-ups started to happen.  All lock-ups happened at night
where activity was pretty low.  We run backup over nfs nightly, and
there is a good chance it is nfs that causes the problem. When the
lock-ups happen backup is usually somewhere in the middle and after
the server is restarted backup finishes ok.

The most strange thing about it is the lock-up itself.  The server
keeps responding to pings, keyboard is working (it is possible to
switch consoles and type, but not log in), there is nothing on console
and in any logs, but nothing else (cron, web server, telnet, ftp,
etc) is working.  Nothing even happens if ctrl-alt-del is pressed on
console.  After the hard reboot everything works fine until next
night.

Anyone has any ideas what can cause the problem? I don't think it is
hardware problem, since server works fine all the day during heavy
load. I suspect that there could be some problem with the amount of
memory, maybe kernel (nfs code?) can't handle situation where cache
gets too big (say, more than 1Gb)...

Any ideas on how to investigate and find the problem will be greatly
appreciated!

Regards,
Sergey Gershtein

--
Ural Relcom Ltd,
Ekaterinburg, Russia


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