Assuming a mirrored (RAID-1) object configuration, how many hosts must contribute storage in a non-stretched
VMware vSAN cluster to satisfy the “Number of failures to tolerate” policy option?
“n” is the desired “Number of failures to tolerate” value for all options.
A.
2n+2
B.
2n
C.
2n+1
D.
3n
Explanation:
If fault domains are configured, 2n+1 fault domains with hosts contributing capacity are required. A host, which
is not part of any fault domain is considered its own single-host fault domain
C
6
1
You configure the Primary level of failures to tolerate (PFTT) attribute in the VM storage policies to handle host failures. The number of hosts required for the cluster is calculated as follows: 2 * PFTT + 1.
In a three-host configuration, you can tolerate only one host failure by setting the number of failures to tolerate to 1. vSAN saves each of the two required replicas of virtual machine data on separate hosts. The witness object is on a third host. Because of the small number of hosts in the cluster, the following limitations exist:
– When a host fails, vSAN cannot rebuild data on another host to protect against another failure.
– If a host must enter maintenance mode, vSAN cannot reprotect evacuated data. Data is exposed to a potential failure while the host is in maintenance mode.
– You can use only the “Ensure data accessibility” data evacuation option. The Evacuate all data option is not available because the cluster does not have a spare host that it can use for evacuating data.
As a result, virtual machines are at risk because they become inaccessible if another failure occurs.
https://docs.vmware.com/en/VMware-vSphere/6.5/com.vmware.vsphere.virtualsan.doc/GUID-57575456-0AD9-4655-9D6B-58509C1DF33C.html#GUID-57575456-0AD9-4655-9D6B-58509C1DF33C
2
0
2n+1
https://communities.vmware.com/thread/463665
3
0