re: UML and HA

[Greg Freemyer <freemyer-ml@NorcrossGroup.com>]

I don't know if it helps with process migration, but you might want to consider the below:

In Compaq's TruClusters they require each process to have a unique pid across the cluster.

They accomplish this by using a 64-bit pid.  Then they have each node assigned a unique node #.

Effectively the pid becomes a simple combination of the node # and the local pid.

in 'c' code:    pid = (node << 32) | local_pid;

          (There are of course faster ways to code this.)

The above may seem extreme, but Compaq seems to have made a major paradigm shift.

They now seem to be designing a high quality/high functionality cluster OS, and let the single node cluster be a special case.

I for one agree with this conceptualization and hope Linux does the same, but I think it will take a lot of evangelizing in the Linux kernel area to see this paradigm take hold.  (I could be wrong here.  I follow Linux clustering mail lists, but not any of the others.)

Greg
=========

Greg Freemyer
Internet Engineer
Deployment and Integration Specialist
The Norcross Group
www.NorcrossGroup.com

>>  I was thinking about HA and process migration, since I've got MOSIX
>>  up and running again, sort of.  One of the problems that all the
>>  process migration systems have is mapping local PID to distant PID.

>>  So here's where user mode linux could come in:  Machines could
>>  pair up in a "buddy system" (or heavier redundancy -- flavor to
>>  taste) and each system would maintain a UML snapshot of what its
>>  buddy is doing.  That way, if the cubans detonate server A, server
>>  R can activate it's UML backup of server A and gracefully handle
>>  server A's business.



>>  -- 
>>  David Nicol 816.235.1187
>>  And the cow threw up seven times, and said:
>>  "Say it now and say it loud, I'm a cow and I am proud."


>>  Linux-cluster: generic cluster infrastructure for Linux
>>  Archive:       http://mail.nl.linux.org/linux-cluster/









Linux-cluster: generic cluster infrastructure for Linux
Archive:       http://mail.nl.linux.org/linux-cluster/