[Xen-users] DomU Locking Mechanism?

[Nathan Eisenberg <nathan@xxxxxxxxxxxxxxxx>]

Hello,

 

I have a new 10 node XEN cluster I've built out using 3.3, and a dedicated iSCSI SAN.  The XEN configuration files are located on a volume on the SAN, which is exported to all Dom0s via NFS.  The system works great, but there is one major issue, and two minor issues which I have to deal with before I take this system into production.

 

The major issue:

I have not found a method that I like for preventing a DomU from being started on two nodes at the same time and clobbering the data.  I've been considering writing a script to manage lock files which are placed into the configuration store directory; these files could contain the hostname of the Dom0 where the DomU is running, which would solve my first minor issue.

 

First minor issue:

I haven't yet found a method for figuring out where DomU's are, short of running lots of xm lists or scripting something silly together.  This hasn't been a problem in my 2-4 node clusters, but it won't work as this cluster scales out to its eventual size (20 nodes).  If I implement the lock file idea, this problem is solvable.

 

Second minor issue:

I recall that there was a way to change the behavior of the XEN daemon so that it would migrate DomUs on shutdown, rather than suspend them to disk.  However, I can't figure out what that was.

 

Third minor issue:

Has anyone developed a mechanism for ensuring that VMs are distributed evenly throughout the cluster?  IE, if I have 10 Dom0s, and 100 of the same DomUs with the same memory size and the same load, the mechanism should ensure that I have approximately 10 DomUs per Dom0.  If a host dies, it'd be nice to have something that figures out how to distribute the 10 DomUs throughout the cluster evenly, so that each Dom0 has 11-12 DomUs on it.

 

A lot of this is probably just scripting, but I suspect this is a road others have had to walk, and I'd just as soon not reinvent a wheel (especially knowing how bad my scripts usually are :-) )

 

I apologize for the length of this post!

 

Best Regards

Nathan Eisenberg

Sr. Systems Administrator

Atlas Networks, LLC

support@xxxxxxxxxxxxxxxx

http://support.atlasnetworks.us/portal

 

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