What happens to the writes that were committed on Host-2 after Host-1 enters this mode?

An administrator has a 4-node vSAN cluster, and all virtual machine storage policies are configured as RAID-1 FTT-1. The administrator puts Host-1 in maintenance mode using "Ensure Accessibility".

During this time, Host-2, which is holding the updated object replica, fails permanently. A few moments later, Host-1 exits maintenance mode.

What happens to the writes that were committed on Host-2 after Host-1 enters this mode?
A . Any writes to Host-2 that occurred after Host-1 entered maintenance mode are lost.
B. The latest writes are retrieved from backups.
C. The latest writes were also written on a third host and are applied to the stale components of Host-1 once the host exits maintenance mode.
D. The latest writes from Host-2 are applied to the stale components of Host-1 once the host exits maintenance mode.

View Answer

Answer: D

Explanation:

This is because vSAN maintains a copy of the object on each host that is a member of the vSAN cluster. When a host enters maintenance mode, the object’s replica is moved to another host in the cluster. If another host in the cluster fails during this time, it’s possible that the updated replica of an object may be lost. However, vSAN will still use the stale replica of the object on the host that exited maintenance mode to service readrequests, and will update the stale replica with the latest writes from the remaining host after the host exits maintenance mode.

It is important to note that this scenario assumes that the host failure is a permanent failure and that vSAN does not have any additional data protection methods enabled such as RAID-5, RAID-6, or Erasure Coding.

The correct answer is

D. The latest writes from Host-2 are applied to the stale components

of Host-1 once the host exits maintenance mode. This is because vSAN utilizes a "write-

order fidelity" mechanism which ensures that any writes that were committed to the other

hosts in the cluster before Host-1 entered maintenance mode are applied to the stale

components of Host-1 as soon as the host exits maintenance mode.

Reference: https://docs.vmware.com/en/VMware-vSphere/7.0/com.vmware.vsphere.storage.doc/GUID-C1E7F9A5-7F5E-4E7E-A012-2F0F19A3F0A4.html