[Xen-users] small cluster storage configuration?

[Miles Fidelman <mfidelman@xxxxxxxxxxxxxxxx>]

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?
Thanks very much,

Miles Fidelman


--
In theory, there is no difference between theory and practice.
In<fnord>  practice, there is.   .... Yogi Berra



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