Path: utzoo!mnetor!uunet!husc6!hao!ames!ucbcad!ucbvax!utorphys.BITNET!SYSRUTH
From: SYSRUTH@utorphys.BITNET
Newsgroups: comp.os.vms
Subject: RE: LAVC help/info request
Message-ID: <8801061734.AA11500@gpu.utcs.toronto.edu>
Date: 6 Jan 88 17:34:00 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The ARPA Internet
Lines: 35


The DELNI has a switch on it (the only switch, in fact) which can be put
in either of 2 positions: 1 to talk to the coax, and the other to keep
communications inside itself (standalone). You can't mix the two. If you are
talking to other machines on the coax, your cluster's communications are
also going out onto the coax, and the DELNI retrieves all packets from
the coax as well. Hence your cluster members lost touch with each other
when you took the coax terminator off. In future, when you plan to do this,
you should flip the switch on the DELNI to standalone *before* killing the
thickwire, and then your cluster won't be affected by the work (it will
not be able to talk to anything not on the DELNI, but then it can't anyway
under those conditions). Your users will only notice this if they are
using terminal servers which are not on the DELNI, but at least the cluster
stays up, which greatly reduces the impact of the work on the system as a
whole.
     
Setting RECNXINTRVL to 300 is likely not a good idea. If one of your cluster
satellite nodes crashes, the remaining members will hang for 5 minutes
attempting to re-establish communications. This may not be a problem if
it can reboot within that time, but if it can't, it's an unnecessary wait.
We don't run an LAVC, but certainly that's how a regular cluster behaves,
and I would expect the LAVC to do something similar. The most obvious reason
I can think of for reducing it from the usual 60s to 20s is so that if someone
shuts down their desktop VAXstation, everyone else isn't sitting around
twiddling their thumbs for so long. Although, again, I'm not that familiar
with LAVC's so there might have been another, more technical, reason.
     
Personally, I'd have been far more surprised if your entire cluster had
stayed up!
     
Ruth Milner
Systems Manager
University of Toronto Physics
     
SYSRUTH@UTORPHYS.BITNET