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

[Bart Coninckx <bart.coninckx@xxxxxxxxxx>]

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
> experiences?
>
> 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.
B.

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