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

On 10/10/11 00:26, 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

Thanks very much,

Miles Fidelman

DRBD does not do 4 nodes. If you split in two clusters you cannot cross migrate, unless you set up the storage on each node in some way, bu thow are you going to replicate?

Personally, I would create a storage cluster and a VM cluster, allowing for epxansion of the virtual nodes later if time/budget permits.


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