Failures to tolerate: how many disks or hosts can fail without losing a VM object, met by mirroring (RAID-1) or erasure coding (RAID-5/6). vSAN's default policy uses one.
Also called failures to tolerate.
Read more: Broadcom TechDocs
In the Ultra Transcenders books
Each book explains FTT in context, with comparison tables and the common traps.
Terms in this definition
- Mirroring
A way of keeping a copy of an outside database, for example Azure SQL Database, Cosmos DB or Snowflake, continuously up to date in OneLake as Delta tables inside a mirrored database. You query it in T-SQL via its SQL analytics endpoint, and the replication compute costs nothing.
- RAID-1
Mirroring in vSAN: whole duplicate copies of an object sit on separate hosts. It handles between one and three failures, at a higher capacity cost than erasure coding.
- RAID-5
Single-parity erasure coding in vSAN, surviving one failure more economically than mirroring. ESA switches adaptively between 2+1 and 4+1, whereas OSA uses 3+1 and so needs four fault domains.
- vSAN
VMware's software-defined storage, which combines local devices across a cluster's ESX hosts into one shared datastore. Available as OSA or ESA, VCF can use it as principal storage.
- Exclusions
Scopes taken out of a policy assignment; they can only narrow its coverage, never widen it.
Related terms
- vSAN Default Storage Policy
Fallback vSAN policy when nothing else is set: thin provisioned, single stripe, FTT=1 and force provisioning off. It cannot be deleted, nor can it be renamed.
- vSAN storage policy
Storage policy with rules specific to vSAN, for example stripe count, space reservation, RAID level and FTT, determining where vSAN puts a VM's objects and how it protects them.