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Multi site san with single subnet

Occasional Visitor

Multi site san with single subnet


I've a design question. I've a total of 10 P4500 nodes. There are 2 physical sites which are connected by dark fiber, so the SAN network is an single subnet. I have a couple of vsphere servers.

Do i need to create 2 sites in the CMC and add node 1,3,5,7,9 to one site and the other 5 in the other site? In this case the multipathing will still work for Vmware because i've only one subnet right?
Or can i just place all 10 nodes in one standard cluster?
Thank you in advance.
Steven Clementi
Honored Contributor

Re: Multi site san with single subnet

If you want a Multi-site Cluster, you need to define a Multi-Site Cluster otherwise... you won't have a Multi-site cluster... and I assume you are splitting your nodes to protect your data in some way. (Being able to set your network raid so that a copy of data lives in both sites)

The other option would be to create 2 standard clusters and then you can replicate your data over to the second site via snapshots/remotecopy.

Steven Clementi
HP Master ASE, Storage and Clustering
MCSE (NT 4.0, W2K, W2K3)
VCP (ESX2, Vi3, vSphere4, vSphere5)
NPP3 (Nutanix Platform Professional)
Paul Hutchings
Super Advisor

Re: Multi site san with single subnet

You need to make sure that your cluster is configured as a multi-site cluster, other than that yes, absolutely correct.

The only thing to note is that if you assign your vsphere servers to a site, they will "prefer" nodes in that site when connecting to the P4000 nodes - typically since you have shared VMFS in vsphere this means that the first server that is booted will connect and that will determine which node is used as the gateway.

My understanding is that that means that if you have 10 nodes (5 in each site) and 10 servers (5 in each site), if you boot the 5 servers in "Site A" first, all of your vsphere iSCSI connection from all 10 servers will only go via the nodes in Site A - nothing will touch the nodes in Site B unless you have a failover.

Happy to be corrected as I'm in a very similar setup just with less nodes (damn you!).
Occasional Visitor

Re: Multi site san with single subnet

I couple of days further testing i think i know how i must set it up:

I create two sites and an logical third site where i place a FOM. The 3rd site is actually at the main location, so when i link failure occurs the main location will stay online.

I place the ESX servers in unassigned site, so they will connect to all Lefthand nodes in both sites. In this way i've a fully redundant SAN on two fysical sites and HA when an Lefthand fails.