Geographically Dispersed Clustering with Clariion

Thanks to Ira Pfeifer for jump starting this topic…I would’ve hit this subject eventually as this has been a rather frustrating experience that I’ve gone through over the years. One of the things that I’ve been pushing for many, many years at EMC is to develop a “GeoSpan” equivalent product for the Clariion environment. In my opinion, our main target audience for CX arrays is the Windows server environments so it seemed like a logical progression for the GeoSpan product to release a similar product for the Clariion line. Symmetrix has SRDF, Clariion has MirrorView. Seemed like a no-brainer to me.

The first sign that this was NEVER going to happen was the name change from GeoSpan to SRDF/CE…SRDF = SYMMETRIX Remote Data Facility so it would’ve been silly to name a product “SRDF anything” if we had plans to incorporate the CX arrays. Next sign was the level of resistance from product management. The PMs kept ignoring my pleas and finally, they asked that I provide a business case scenario showing the market for such a product…this was management’s way of politely telling me to go away. They were fully aware that I was a technical resource and it would be unlikely for someone like myself to provide the necessary logistical information to pursue this further.

Unfortunately for them, I actually do have the vision and desire to see such a thing through and could not be swatted down by some menial paperwork. I found a dozen different customers that have requested exactly this type of product and I submitted a pretty decent case to the different product groups. This got some attention and the developers from the MirrorView team were engaged by the SRDF/CE team to research the feasibility for such a software product. The outcome was that the MirrorView APIs were not capable of handling the types of commands necessary for a GeoSpan equivalent product and it would require a total rework of the MirrorView coding to make this functional. In the end, this idea was rejected even though this is really something we should be providing to our customers.

With that said, it is still possible to setup a geographically dispersed cluster using Clariion with MirrorView with Windows 2003. One of the main reasons why we were told that MV/CE (my name for the SRDF/CE equivelant for MirrorView) couldn’t be done was that MV couldn’t handle the quorum arbitration needed to support a geocluster. If you use a MNS quorum, there’s no need for MV to get involved with the quorum arbitration. You could build a MNS cluster and then create a generic script or application resource to control the MirrorView failover. You would create your physical disk resources and make then depend upon these generic app/script resources and voila…you now have a geographically dispersed MirrorView cluster. If you’re not familiar with NaviCLI commands, I’ve been told that you could contact EMC professional services to help you develop these scripts…some customers are actually doing this today in their environment. 

I spent a little bit of time trying this last week and I successfully setup this type of configuration in my lab environment so I know that this is possible. Now whether or not such a thing would be supported…from an EMC perspective, you would need to submit an RPQ for support from EMC. For MSFT support, this would need to pass HCT testing and submit it to MSFT for review. I do not think there are currently and MirrorView clusters in the Windows Catalog yet.

Another possibility for the Clariion environment would be to use NSI’s GeoCluster or DoubleTake to create host-based mirrors over IP. This is something I plan on testing myself in the next couple of weeks. Stay tuned for those updates.