RE: [Xen-users] Xen SAN Questions

[John Madden <jmadden@xxxxxxxxxxx>]

> > Well, first off, ask yourself why you're using a cluster filesystem in
> > the first place.  Do you have active-active writers on the same
> > filesystem at the same time?  If the answer is no, then get rid of GFS
> > -- you don't need it.
> The reason for this was so that I could have two Xen hosts using  
> their local storage but to also have it replicating between servers  
> for backup purposes. Maybe I was going about this the wrong way, but  
> I wanted to have the ability to use the large storage pool (created  
> by the cluster) as a platform for storing VMs as well as have it  
> back everything up on two separate locations of disk.
I think DRDB will work here (never used it personally), but I think  
I'd create a DRDB device for each VM and replicate each one separately  
so you could have a primary on the remote side running a vm that can  
be started locally if the remote site blows up and vice-versa.  You  
don't need the added overhead of a cluster filesystem for this.  DRDB  
will certainly add overhead for replicating writes, but this is highly  
tweakable (consider you're replication write rate, for example, where  
maybe you're writing to the disk at 100MB/s but only replicating at  
10KB/s, thus saving a ton of i/o).
> To clarify, the disks themselves will be a RAID-5 local to each  
> machine (1 array per machine, 2 in total) with DRBD running between  
> to sort of RAID-1 them over the network. Does that help? I want to  
> take the local RAID from both machines and turn it into a SAN.
Cool, that's fine, but don't say "SAN" here, they're different.

John





--
John Madden
Sr. UNIX Systems Engineer
Ivy Tech Community College of Indiana
jmadden@xxxxxxxxxxx


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