VMworld 2015/Building a Stretched Cluster with Virtual SAN

Building a Stretched Cluster with Virtual SAN

By Duncan Epping and Rawlinson Rivera (VMware)

“A stretched cluster is a deployment model in which two or more virtualization host servers are part of the same logical cluster but are located in separate geographical locations.”

Metro Clusters

vSphere + Virtual SAN – Stretched Cluster

Fault Domains – (data, data, witness)

Virtual SAN cluster is formed across the 3 fault domains (sites or datacenters)

Requirements:

• Network:
  • Virtual SAN storage networking
  • Virtual SAN witness networking
  • vSphere and virtual machine networking
  • 10 Gbps connectivity or greater
  • < 5 millisecond latency RTT
  • Multicasting
• Storage:
  • Virtual machine storage
  • Witness appliance storage
• Compute:
  • Virtual SAN witness
  • vSphere HA
  • vSphere DRS

Witness only stores metadata. Communication to it is minimal.

Steps to build a stretch cluster:

• Configure Fault Domains
• Select Witness Host
• ?
• ?

Virtual Machine Monitoring – the core of the heart beating for HA

• If doing maintenance, disable this

Reserved failover capacity resources – set to 50% (yes you lose half your resources!)

Test Test Test - Test all of the various failure scenarios you can have

• Network partition between data sites
• Full site failure
• Witness site failure

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