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V series Cluster with more than 2 storage systems?

Hello,

we plan to implement a fabric attached Metro Cluster with two V series or better N series Gateways. Customer is thinking about to bring the mirrors of both to a third box or a third and fourth box. The storage system is the same, same modell, same MC level etc.

To explain this a little bit better I attach a very rough picture, just to show the plan.

For the plan with the third side they have the two nodes. The local storage is attached to the node and holds the data, the mirrored data from the synch mirror lays on a third box in a third DC, there is alsways one hop to the data.

So the question is, is it possible to store the mirror for both nodes on a third, completely independent box or is it only possible when local data and mirror data from the partner node are on the same storage box.

Same for the second scenario where the Node have the data on the local storage and the mirrored data are on an other storage box in the other DC and vive versa. The data are in diefferent sites and are reachable over one hop always, but not on the same storage system as the local data from the partner node.

In both scenarios the storage systems are DS8k with same characteristics, same setup, same MC level etc.

Are this scenatios support or are there any concerns?

Thanks in advance!

Regards Falk

Re: V series Cluster with more than 2 storage systems?

It is not possible using cluster and SyncMirror. Cluster consists of exactly two nodes and in any case mirrored aggregate consistes of exactly two plexes.

What may be possible is to use SnapMirror Sync to replicate data to the third filer. In this case failover/failback will not be automatic (at least, from NetApp side) and requires careful planning.

Re: V series Cluster with more than 2 storage systems?

Hello aborzenkov,

thanks for your fast answer, but it seems that there is a misunderstanding.

It is not the plan to mirror to a third filer. What we plan is to have the local data from Node 1 (Plex 0) at the local storage system, in the picture DS8k -A, and the mirror of this (Plex 1) on the DS8k -C in the picture.

For node 2 we again have the data of Plex 0 local (DS8k - B in the picture) and the Plex 1, the second part of the mirror also on DS8k -C at a third location. So the Plex 0 are always local at the same location like the owning nodes, but the mirrors (Plex 1's) on a thirsd independent storage Box. Is this possible? Or have the plex 1 of node 2 at the same site/Box as Plex 0 of Node 1?

Its similar with the 4 site scenario. There we again just want to spread the Plex 1 of the local sync_mirror on an other box. would this be also possible?

Thanks!

Re: V series Cluster with more than 2 storage systems?

Sorry, there was misunterstanding indeed.

Yes, I believe both your diagrams are possible; I'd still get support statement from your NetApp representative though

Re: V series Cluster with more than 2 storage systems?

Hi Falk,

Interesting idea.  I'm not sure of the problem that it solves, though.  The point of a MetroCluster is to survive the loss of one datacenter.  Throwing a third into the mix is unnecessary to achieve the same level of resiliency.  Is it the capacity they gain from a third array?  Could burn up a lot of ports, as both controllers would need at least 2 paths (each) to every array.  Possibly more, depending on the number of LUNs.

This would probably work, but I can't think of any customers that are doing it.  We would need a PVR to give us an opportunity to review the configuration and ensure it was something that NetApp could support.

Sorry I can't provide a better answer than that, but that's the correct answer. 

Dan Isaacs

NetApp

V-Series TME

isaacs@netapp.com