VMware Metro Storage Cluster Overview

VMware Metro Storage Cluster

VMware Metro Storage Cluster (vMSC) allows vCenter to stretch across two data centers in geographically dispersed locations. In normal circumstances, in vSphere 5.5 and below at least, vCenter would be deployed in Link-Mode so two vCenters can be managed as one. However, with vMSC it’s possible to have one vCenter manage all resources across two sites and leverage the underlying stretch storage and networking infrastructures. I’ve done previous blogs on NetApp MetroCluster┬áto describe how a stretched storage cluster is spread across two disparate data centers. I’d also recommend reading a previous post done on vMSC by Paul Meehan over on The idea behind this post is to provide the VMware view for the MetroCluster posts and to give a better idea on how MetroCluster storage links into virtualization environments.

The main benefit of a stretched cluster is that it enables workload and resource balancing across datacenters. This helps companies to reach almost zero RTO and RPOs and ensure uptime of critical systems as workloads can be migrated easing using vMotion and Storage vMotion. One thing to keep in mind regarding vMSC, it’s not really sold as a disaster recover solution but rather a disaster avoidance solution when linked with the underlying storage. Some of the other benefits of a stretched cluster are:

  • Workload mobility
  • Cross-site automated load balancing
  • Enhanced downtime avoidance
  • Disaster avoidance
  • System uptime and high availability

There are a number of storage vendors that provide the back-end storage required for a vMSC to work. I won’t go into the entire list but you can find out more on the VMware Compatibility Matrix site. The one that I have experience with is NetApp MetroCluster but I know of others from EMC and Hitachi at least. So what components make up a vMSC? It comes down to an extended layer 2 network across data centers so that vMotions can take place with ease and also a resilient storage platform connected to ESXi via VMFS or NFS datastores. VMware vCenter itself does need some configuration changes but it’s nothing outside the scope of what a regular VMware admin can implement. A view of what a vMSC looks like is below. The networking and storage components have been simplified.

fabric metro cluster diagram


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