2 server rooms on one "site" or 2 sites

normally you would considered two seperate sites if the Server Rooms are in different buildings, at least 6km apart.

If you had a disaster in your case both servers room would be out of action, fire, flood, explosion, hurricane etc

But you can easily use Hyper-V 2012 to replicate VMs between servers and storage.

I "third" the opinion..  There is NO NEED to create a second site, unless you have a slow or unreliable link in between 2 locations.. It's just not worth the headaches, unless you have some other strange reason to create a site...  I have 2 data centers that are in different states, but we have fiber directly between them w/ multi-gig speed and 2ms latency, and  I have those in the same site, and support 30k users out of them, and have no problems at all, even for (or maybe ESPECIALLY FOR) Exchange replication..

I have had to create separate sites when:
1:  Management demanded that the users and Exchange servers use separate DCs to authenticate, so we were forced to create an "Exchange site" which was eventually done away with because there was no benefit, and a lot of added replication complexity and extra DCs.
and
2:  During an Exchange migration we had a strange need to proxy external OWA, and the CAS servers wont proxy to another CAS Server unless they think they're in a different site, so I had new DCs built and put host addresses (/32) in the separate site to force 2 specific CAS servers to THINK they're in a different site so they'd proxy instead of redirect..  This was a total kludge created by some security requirements and the certificates/URLs we were forced to use, and was ONLY for the duration of the migration..

Aside from that, ALWAYS make one site unless you can prove a need otherwise..  You'll be happier in the end!!

I have a 10gb ip data network and an 8gb SAN data network, so latency and bandwidth are fine.

I've been looking at Hyper V 2012 multi-site clusters with the idea that site 1 replicates to site 2 and site 2 replicates to site 1, as both have active resources within them, however I can't figure out the storage setup for this. How does each site know when the other has failed to turn the replica storage into active?

I agree 1 site is easier to manage, but with that I can have VMs running on a san from either location with no logical separation.

Thanks for the input.

By "Site", I'm trying to establish as to whether we should do a multi-site cluster of hyper V (basically 2 clusters, 2 sans with san replication) or just group all nodes into one well-named and documented cluster for ease of management.

System Center VMM will allow us to manage the two clusters as a multi-site cluster, but automatic failover will still depend on us breaking the san lun mirroring.

We could also look at "live" volumes where the SANs decide which SAN holds the RW copy of a particular lun, but this may introduce split brain nightmares.

If i try to clarify my question:

Considering two equal server rooms on a single site with 10gb data and 8Gb fibre (SAN) links which appear to have been designed for active/active operation, should my new virtualised environment based on hyper v 2012 be configured as one cluster per server room, or a large cluster which spans both server rooms?

Thanks.

Thanks everyone for your input.

We're going with one large cluster and single site with GOOD documentation and naming on cluster nodes, luns, etc purely for the ease of management and failover etc.

Thanks for the opinions.