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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