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Tuesday, 15 August 2017

What is PFTT and SFTT in VMware vSAN 6.6

In vSAN 6.6, new storage policy features have been added for stretched clusters. These features provide failure protection for stretched clusters: 
Local Protection for Stretched Clusters
  • Primary level of failures to tolerate (PFTT) replaces the previous Failures to Tolerate (FTT). It applies to tolerate the failures across sites of streched cluster
  • Secondary level of failures to tolerate (SFTT) is a new rule that applies to tolerate the failures within each site of a stretched cluster. 
Note: SFTT is only available when streched cluster is configured, as vSAN capability for creating the vSAN Storage Policies
  • The failure tolerance method is tied to the SFTT rule as it defines how failure tolerance is achieved within each site but not across sites.
  • One can have PFTT = 0, SFTT = 1 or 2 either they can have PFTT = 1, SFTT = 1 or 2.

RAID 5/6 Erasure Coding in Stretched Clusters
  • RAID 5/6 erasure coding is only supported within each site.
  • RAID 1 mirroring is supported cross-site.
Image thanks to VMware