Re: Interesting cluster config "deadlock"

I know some full production environments that have been like this for
many months (years?)
I managed an environment where a VAX with locally attached DSSI disks
was clustered with a pair of turbolasers with shared SCSI. The VAX
needed stuff from the Alphas to boot and the Alphas needed stuff from
the VAX.
We also needed to retain cluster quorum.
Ultimate answer was to bring up the one Alpha with very little
starting. Then bring up the VAX and the other Alpha, then reboot the
first Alpha.
Messy, but it worked.

Steve

JF Mezei wrote:
The local transformer blew its fuse on a very cold winter day. I was
litterally powerless to keep my systems running.

Upon rebooting, I found myself in an interesting situation. Being in the
(slow) process of moving stuff and restructuring my cluster, I found out my
cluster had been left in a precarious state !

SYSUAF (et all) was still on a node1 disk. User disk is on node2, but node2
boots off node3.

node1 was still in charge of defining certain clusterwide logicals pointing
to disks now served by node2. So when node1 booted, those disks were not
available and the logicals were missing a device name :-)

Amd because of cluster quorum, I could not sequentially boot the nodes in
the right order. Node1 had to wait for enough other nodes to boot befor
continuing its boot process. And once enough votes were present, the order
of booting was dictated by system speed.

In the end, I managed to get it all up, but it required reoots of some
machines once the other machines were up and able to serve the good disks.

This is something I had not considered before.

So now there is a bit more pressure on my derrière to complete my cluster
reconfig and make it robust enough to be able to recover fully
automatically from a power failure.

Just something to keep in mind when moving stuff around in a cluster.

.

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