4 Server XenServer Pool and HP P4300 4 node cluster

[SSMIC]

Hi everyone!

Currently I have a 4 node P4300 Cluster and would like to use the storage to it's maximum potential, meaning that I would like to  have the XenServer pool. connect to multiple nodes at the same time for increased performance. I have read all the best practices and the many older posts regarding Xenserver and HP P4300 StorageWorks and just want to ask you all if I am on the right track here.

My plan is to run four BL460c Blades with Xenserver Enterprise 6.x with my HP P4300 G2 four node cluster. I want to take advantage of the MPIO/DSM and have my VM utilizing the full power of my four node cluster in that it makes a connection to each of the nodes for performance and redundancy. Now I guess my question is this does the XenServer itself make those connections or does the VM make those connections to the cluster for each SR hosted on the cluster? Currently when I connect to a shared SR there is only ever one (two if i have multipath enabled) but only to one storage node in the cluster. So when I do a rolling update my VM's go down.

I hope Im have explained myself OK!

Thanks for your time!

Gerry

[Dirk Trilsbeek]

all your systems should always only connect to the Cluster VIP of your Lefthand Cluster. The Cluster VIP will be available as long as the cluster itself is available. If the system currently handling the VIP goes down, another node will step in and take over.

Connecting to the VIP means the systems will be redirected to the node handling the LUN that was requested. If the node that handled that LUN also has gone down, the request will be redirected to the node that took over that LUN. So in general if your cluster is alive (quorum available), you should not experience any downtime. Make sure you run a Failover Manager in your cluster, especially with an even number of nodes.

[SSMIC]

Dirk,

Thanks for the reply. I am indeed using the VIP when connecting to the SR and cluster but when I open the CMC for the SAN the server only shows the Xenserver connected to a single node not to all of them such as any of my other windows servers which shows at least 5 connections, one to each node and a spearate DSM connection.

So If I am understanding you correctly then even if it shows the single connection to the node and I do a rolling update the connection will resume onto another of my nodes? And yes I have a FOM as well M of N works best with odd numbers. Thanks for the advice!

[Dirk Trilsbeek · Accepted solution]

thats right. There will of course be a short disconnect from the node that is restarting, but as soon as the XenServer tries to reconnect (and goes back to the VIP), it should be redirected to another node. We have a VMWare environment and our servers use several NICs for iSCSI, but they all connect to the same node. We did several updates where each node had to be restarted and we never experienced any downtime during the update.

[5y53ng]

Like Dirk said another storage node will assume handling IO for your volumes. This is accomplished via iSCSI login redirect. With older versions of SANiQ you would see a little hesitation when gateway connections changed, but now it's a virtually seamless transition.

[SSMIC]

Thank you both for your answer!