[Gluster-users] configuration questions & advice

[Miles Fidelman]

Hi,

I have a small cluster that I use to host a collection of Xen virtual 
machines.  I just expanded from 2 nodes to 4 nodes and am looking for 
some advice re. configuring a storage subsystem.

The current (2-node) configuration is simple:
- 4 disks per node
- md-based raid
- lvm
- DRBD to replicate (some) volumes between the two nodes
- (some) VMs set up for auto-failover on node failure (pacemaker, etc.)

In moving to 4 nodes, I'd like to add some flexibility to move VMs 
across all 4 nodes, but... that requires using something other than DRBD 
to replicate volumes.  I'm thinking of something with the following 
characteristics:

- 4-node storage cluster (4 drives per node, total of 16 drives in the 
storage pool)
- 4-node VM cluster
- using the SAME 4 nodes for both
- note: I've got 4 gigE ports to play with on each box (plan on using 2 
for outside access, 2 for storage/heartbeat networking)

GlusterFS stands out as the package that seems most capable of 
supporting this (if we were using KVM, I'd probably look at Sheepdog as 
well).

So... a few questions:

- it looks like running replicated volumes, across 4 nodes, will provide 
for redundancy and support migration/failover (am I right in this? or 
should I be looking at running RAID on the individual nodes as well?)
- what kind of performance hit is involved in replicated volumes?
- is there anything more efficient in disk use (i.e., mirroring 4 copies 
eats up lots of disk, is there anything equivalent to RAID 5/6 that is a 
little more efficient while maintaining redundancy?)
- am I missing anything (either re. GlusterFS or other alternatives)

Thanks very much for any suggestions and advice.

Miles Fidelman

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