Re: [Xen-users] small cluster storage configuration?

[Iustin Pop <iusty@xxxxxxxxx>]

On Sun, Oct 09, 2011 at 06:26:18PM -0400, Miles Fidelman wrote:
> Hi Folks,
> 
> I've been running a 2-node, high-availability cluster for a while.
> I've just acquired 2 more servers, and I've been trying to figure
> out my options for organizing my storage configuration.
> 
> Basic goal: provide a robust, high-availability platform for
> multiple Xen VMs.
> 
> Current configuration (2 nodes):
> - 4 drives each (1TB/drive)
> - md software raid10 across the 4 drives on each machine
> -- md devices for Dom0 /boot / swap + one big device
> -- 2 logical volumes per VM (/ and swap)
> -- VM volumes replicated across both nodes, using DRBD
> -- pacemaker, heartbeat, etc. to migrate production VMs if a node fails
> 
> I now have 2 new servers - each with a lot more memory, faster CPUs
> (and more cores), also 4 drives each.  So I'm wondering what's my
> best option for wiring the 4 machines together as a platform to run
> VMs on.
> 
> Seems like my first consideration is how to wire together the
> storage, within the following constraints:
> 
> - want to use each node for both processing and storage (only have
> 4U of rackspace to play with, made the choice to buy 4 general
> purpose servers, with 4 drives each, rather than using some of the
> space for a storage server)
> 
> - 4 gigE ports per server - 2 reserved for primary/secondary
> external links, 2 reserved for storage & heartbeat comms.
> 
> - total of 16 drives, in groups of 4 (if a node goes down, it takes
> 4 drives with it) - so I can't simply treat this as 16 drives in one
> big array (I don't think)
> 
> - want to make things just a bit easier to manage than manually
> setting up pairs of DRBD volumes per VM
> 
> - would really like to make it easier to migrate a VM from any node
> to any other (for both load leveling and n-way fallback) - but DRBD
> seems to put a serious crimp in this
> 
> - sort of been keeping my eyes on some of the emerging cloud
> technologies, but they all seem to be aimed at larger clusters
> 
> - sheepdog seems like the closest thing to what I'm looking for, but
> it seems married at the hip to KVM (unless someone has ported it to
> support Xen while I wasn't looking)
> 
> So... just wondering - anybody able to share some thoughts and/or
> experiences?

Have you tried Ganeti (http://code.google.com/p/ganeti)? It uses DRBD
under the hood but it manages moving instances around without you having
to reconfigure instances. I think it matches what you're looking for,
and we support clusters from 1 physical machine up to hundreds.

Disclaimer: I'm one of the authors.

regards,
iustin

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