Cross-Site SAN Streched Cluster Pros n Cons

before you even discuss fabric connectivity, how are you going to share the storage ? Cluster nodes need to have access to the devices, so if your array is at site A and cluster nodes are at site A and site B ..if site A offline ..having cluster nodes at site B won't get you anything.  Are you doing SRDF/ MirrorView and this is going to be part of the solution ?

1. Using transit VSANs over IVR is the preferred way, since a link failure doesn't cause an RSCN which could possibly distrurb your connections in the data centers. Only within the VSAN where the failure occured the RSCN is being triggered. A full stretched VSAN maybe easier to implement (and cheaper), but if the link somehow fails (bulldozer or something) you'll end up having 2 VSAN entities with the same identity who are orphaned and need to merge again when the link is online again. If the line starts going up/down/up/down/up/down/up/down/up/down, you can imagine that this eventually will be disruptive.

2. Performance ? Switching speed is way faster that true routing speed. It's microseconds... don't worry about that. IVR is great.

3. Put the LW port in the transit VSAN (on each side) and connect the two using SM fiber. This fabric should now be online (a VSAN is a fabric). Go ahead and create an IVR using the transit VSAN you just created and connect to the (local) VSAN on the other side.

Good point ! I assumed some common sence and totally forgot about this

You will need something like SRDF/CE or MirrorView/CE when you're using windows clustering.

Hi Guys,

I have tried to create a diagram and yes ofcourse we have storage available at both sites and now we got to plan for mirroring and the option is to use either mirrorview cluster enabler with SRDF or Host based mirroring.

I hope you can get the idea now wid a picture.

Mirrorview is for Clariions, SRDF is for DMX/VMAX, so whatever storage array you have, this is the replication you will use.

Hi RRR,

I was told that mirrorview Cluster enabler works on both MirrorView(Clariion) and SRDF(DMX/VMax) and this tool would be responsible for the cluster failover b/w the sites.

I was more concerned on the Streched Switch Fabric and make sure, we follow the best practices available for the same.

3. Put the LW port in the transit VSAN (on each side) and connect the two using SM fiber. This fabric should now be online (a VSAN is a fabric). Go ahead and create an IVR using the transit VSAN you just created and connect to the (local) VSAN on the other side.

i would not put long waive ports into transit VSAN, keep LW ports in VSAN 1 and simply "trunk allow" your transit VSAN. If you move your LW port into transit VSAN and somebody accidentally deletes that transit VSAN, the port will be moved to VSAN 4094 and go down. If you were trunking multiple VSANs over that interface ..all VSANs go down.  If you keep LW ports in VSAN 1 you are safe ..you can't delete VSAN 1 even if you wanted to.

Ah ok, you’re right. I was in doubt about VSAN 1 and what I wrote. Both work, and my conclusion was that since it’s a transit VSAN it doesn’t really matter in what VSAN the LW ports are. But putting every ISL in VSAN 1 makes more sence.

Ah ok, I wasn’t aware that both CEs is in fact just 1 and works with both MV as well as SRDF.