Which statement is true about vSAN three-node cluster configuration?
A. Three-node clusters can tolerate a maximum of 2 host failures as long as there at least 2 disk groups in each host.
B. A storage policy with a RAID-5/6 erasure coding rule cannot be applied to a virtual machine object.
C. A storage policy with a deduplication and compression rule can be applied to a virtual machine object.
D. Three-node clusters can tolerate a maximum of 2 host failures.
Correct Answer: BC
Explanation/Reference:
Explanation:
B – It’s true that RAID 5/6 erasure coding can only be enabled for all flash configurations. But the question does not specify if it’s a hybrid or all flash configuration. Also erasure coding setting is not a vm base setting its cluster base setting.
3-Node Configurations
While vSAN fully supports 2-node and 3-node configurations, these configurations can behave differently than configurations with 4 or greater nodes. In particular, in the event of a failure, there are no resources to rebuild components on another host in the cluster to tolerate another failure. Also with a 2-node and 3-node configurations, there is no way to migrate all data from a node during maintenance. In 2-node and 3-node configurations, there are 2 replicas of the data and a witness, and these must all reside on different hosts. A 2-node and 3-node configuration can only tolerate 1 failure. The implications of this are that if a node fails, vSAN cannot rebuild components, nor can it provision new VMs that tolerate failures. It cannot re-protect virtual machine objects after a failure until the failed components are restored. Design decision: Consider 4 or more nodes for the vSAN cluster design for maximum availability Multiple disk groups and 3-node clusters
Another advantage of multiple disk groups over single disk group design applies to 3-node clusters. If there is only a single disk group per host in a 2-node and 3- node cluster, and one of the flash cache devices fails, there is no place for the components in the disk group to be rebuilt. However, if there were multiple disk groups per host, and if there is sufficient capacity in the other disk group on the host when the flash cache device fails, vSAN would be able to rebuild the affected components in the remaining disk group. This is another consideration to keep in mind if planning to deploy 2-node and 3-node vSAN clusters.
Answer = “B” by itself. RAID-5 requires a minimum of 4 Hosts whereas RAID-6 requires a minimum of 6 Hosts.
“C” would be incorrect as Dedupe & Compression are defined at the Cluster-level and **not** at the Storage Policy Level.
“Note that there is a requirement on the number of hosts needed to implement RAID-5 or RAID-6 configurations on VSAN. For RAID-5, a minimum of 4 hosts are required; for RAID-6, a minimum of 6 hosts are required”
Source –
* VSAN 6.2 Part 2 – RAID-5 and RAID-6 configurations – CormacHogan.com
https://cormachogan.com/2016/02/15/vsan-6-2-part-2-raid-5-and-raid-6-configurations/