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Best Practices with VMs in Clusters
Our organization has about 130 SQL instances. Most are VMs (on Hyper-V). The more mission-critical VM SQL instances are failover-clustered. The VM hosts themselves also consist of failover-clusters. So we have: SQL on a cluster, which is built out of two nodes (each on a different VM host), Each host is running on a two-node hardware cluster. Belt-and-suspenders redundancy by design. My boss's boss wants me to discover whether this is too redundant - whether we are setting ourselves up for a glitch or failure, that should by common knowledge within the Windows and SQL Server community. Using Google, I haven't found much that would be definitive, or even an example of anyone else doing this. Anyone have experience or knowledgable opinions to share? Thanks, Mike Hinds
Jonathan Kehayias has some good blog posts on clustering on top of VMs [
http://www.sqlskills.com/blogs/jonathan/clustering-sql-server-on-virtual-machines-round-2/][1] [1]:
http://www.sqlskills.com/blogs/jonathan/clustering-sql-server-on-virtual-machines-round-2/
Hi Mike, The new geo-clustering features in Windows Server 2008 R2 mean you no longer need a stretched v-lan to implement geo-clustering which works well with AlwaysOn availability groups. For example you have a 2 node cluster at site A and a two node cluster at site B which are part of the same cluster group and share an Availability Group Listener. Both nodes at each site share a SAN and can only failover between nodes at that site. AlwaysOn syncronizes the data with the primary site/primary node to the standby site/primary node. Depending on the performance you need from your database servers, running SQL in a VM has only very recently become really viable -
http://www.brentozar.com/archive/2013/01/big-changes-for-big-virtual-machines-in-vmware-vsphere-5/. with the new vNUMA feature. There's a good book 'Pro SQL Server 2008 Failover Clustering' with a chapter on virtualization that might be useful for you. Hope this is useful, Paul
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