TommyB1972
Contributor
Contributor

vSAN HA stretched cluster

Hi,

Currently learning about vSan. I have some questions.

Is is best practice to also have running VM's on the VSAN host?

I would like to create a 2 node stretched vsan cluster with 1 witness node.
So one VSAN in location A and one VSAN in location B.
Configure HA on the nodes hosting the VM's.

 

  1. How much data loss will i have when a ESXi host in location A goes down.
  2. Will the data replication between the 2 vSan nodes be synchronized a a-synchonized?
  3. Where do i place the witness node?

 

Thanks for the help.

0 Kudos
2 Replies
TheBobkin
VMware Employee
VMware Employee

@TommyB1972 
"Is is best practice to also have running VM's on the VSAN host?"
I am not really sure what the point of having hosts at all would be if you were not going to run VMs on them!

"How much data loss will i have when a ESXi host in location A goes down."
So the main point of 2-node clusters (and vSAN in general for the most part) is that data has some redundancy and is not lost when a single node/disk/Disk-Group becomes unavailable - think of it as RAID1 across nodes, with a replica of all data stored on each node and small metadata stored on the witness (only used as a tie-breaker). Thus if you have standard FTT=1 Storage Policy applied to the data then no data will be lost.

"Will the data replication between the 2 vSan nodes be synchronized a a-synchonized?"
Synchronous - IOs are not committed until cache-tier on both nodes writes the data and acks.

"Where do i place the witness node?"
Anywhere really (except on the data-nodes) - this doesn't have beefy hardware nor low-latency network requirements, typically vSAN customers run these in the cloud or on some other VMFS/vSAN infrastructure.

0 Kudos
depping
Leadership
Leadership

there's a pretty extensive Stretched Cluster guide to be found here:

https://core.vmware.com/resource/vsan-stretched-cluster-guide

0 Kudos