VMworld 2014/Performance best practices to run virtualized applications on Virtual SAN

Benchmarking VSAN 101:

• Give time for SSD cache to warm up
• Monitor performance metrics on each host
• Look out for odd situations:
  • read cache hit rate when working set doesn't fit in SSD
  • de-staging performance for "write" workloads
  • distribution of vmdks across cluster
  • SSD and MD (magnetic disk) IOPS and bandwidth
  • spikes in latency due to sudden MD accesses
  • CPU bottlenecks

Tools:

• VSAN Observer (KB 2064240)
• Esxtop
• Ruby vSphere Console (RVC) - fling

VSAN Observer:

• Check the Read Cache (RC) Hit Rate

Configuring for Performance:

• SSD very important - check both read and write performance
• Controllers - queue depth and on-board cache
• MD (Magnetic Disk) - faster disk helps with de-staging
• VSAN Hardware guidance (doc? site?)
• Sizing of SSD to MD ration, must hold as much working set as possible
• Stripe width - go higher than 1 if % of VMs IO served from read cache is low

Microbenchmarks show:

• excellent read performance
• mixed read/write workload performance depends on working set size and performance of SSDs/MDs