Site-Aware Clustering

by | Oct 1, 2018 | Infrastructure | 0 comments

Perhaps you’ve created a cluster in your data center but still have the nagging concern – what if we lose the site?  Windows Server 2016 can help with site-aware clustering and leveraging your witness in the cloud.

What is site-aware clustering?

Site-aware clustering allows for stretched clusters to be set by physical location. You can stretch your cluster across data centers and have failover configured for separate sites.

Some of the features of site-aware clustering are:

  • Site affinity
    • A group will first attempt to failover to another node in the same site.
    • If performing a node drain, VMs will first attempt to move to a node in the same site.
  • Configurable site heartbeats
  • VMs follow their storage. For example, if storage is moved to a new site, the VMs will migrate to that site after a minute or so.
  • A site can be designated as a Preferred Site
    • If there is a Quorum Split (even split of voting members in the two datacenters with no witness), the Preferred Site is automatically elected to win.
    • Each group can have its own Preferred Site for additional flexibility.
    • The Dynamic Quorum will adjust the DR site’s votes first to ensure that the Preferred Site survives if all things are equal.

Cloud Witness

You can also leverage your Azure subscription for a cloud witness.

  • It determines which site is really active in the case of circuit failure; no split-brain or reverting to preferred site if not desired.
  • This is a good option for those without a third location – you can put witness server in by utilizing Microsoft Azure.
  • It is a low cost solution since only using Azure Blob Storage; no need for a virtual machine.
  • Multiple clusters can use the same Azure Storage Account without a conflict as each cluster will use a unique id for the blob file name.
  • The cloud witness is an option built into Server 2016 Cluster Quorum Settings.

Having resources constantly available can be a challenging and costly undertaking. With site-aware clustering you can leverage your company’s already existing sites to build out your disaster recovery and business continuity plan!

Need more information or assistance in leveraging Azure? Email  We are happy to help.