VSAN-Troubleshooting-Reference-Manual

Diagnostics and Troubleshooting Reference Manual – Virtual SAN
Take the following example of a Virtual SAN 6.0 deployment, which has a virtual
machine, deployed with NumberOfFailuresToTolerate = 1 and
NumberOfDiskStripesPerObject = 3. In this the votes are distributed such that we can
still guarantee virtual machine access in the event of a failure without the need for
witnesses:
Note that at least “2n+1” hosts are needed to be able to tolerate “n” number of
failures in the cluster. If the data components of an object do not span 2n+1 hosts,
witnesses will still be needed in Virtual SAN 6.0. This appreciation of the
relationship between virtual machines, objects and components will help with
understanding the various Virtual SAN failure scenarios.
This table may also help you to understand the relationship between
NumberOfFailuresToTolerate, component count and witnesses in Virtual SAN 5.5.
Number Of
Failures To
Tolerate
Component
count
Number
of hosts
needed
Component
types
Number of
components needed
for object availability
0 1 1 1 x Replica 100% or 1 component
1 3 3
2 x Replica + > 50% or 2
1 witness components
2 5 5
3 x Replica + > 50% or 3
2 witness components
This next section looks at the different ways in which objects and components are
affected by errors in Virtual SAN.
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