A vMSC – perhaps more commonly known as a “metro cluster” –  is an architecture in which individual vSphere clusters will be spread across multiple geographical sites.  Since a vSphere cluster requires shared storage to allow VM’s to migrate across hosts, in a vMSC environment this will mean that storage must be shared or replicated across the geographical sites.  As you might expect, this kind of architecture comes with a number of gotchas and limitations, especially around the configuration of the storage arrays.  For this reason, storage vendors who support vMSC architectures have released best practices documentation specifically for designing vMSC’s with their storage products.

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