Hello suhag79,
"Expected IOPS requirement from app team is 15000 IOPS for all the VMs to be hosted"
Weird - it showed as 9k IOPS a moment ago, what changed?
"I read that vSAN ready node HY-6 series (CISCO C240 M4SX) can provide up to 20K IOPS"
Source of where you read this please.
This would almost certainly be IOPS per node as there is no way of knowing how many hosts in a cluster - e.g. if you had 8 nodes in a cluster instead of 4, a per-cluster performance estimate would make no sense.
Do note that these 'up to' figures are usually done using the optimal configuration (e.g. more expensive/better disks, controllers etc.) unless otherwise specified (e.g. for a Ready-Node model that has no configurable options such as better disks).
This also assumes optimum workload characteristics such as IO size and usage-pattern.
Typically don't take any 'up to' performance as gospel - test the actual IOPS this cluster is capable of using a tool such as HCIBench.
"For example, if i have only one VM running on vSAN node-1, can that VM get whole ~ 20K IOPS ?"
If you have a non-striped FTT=1 Object this could at most use the IO performance of 2 nodes (as only 2 would be storing data-components), *potentially* if this was striped in such a manner across all hosts (e.g. 2x RAID0 mirrors each over 2 hosts, no witness components) this could use 4 hosts output but I don't think there is a way to force stripe-placement as such.
There are mechanisms in place to not starve other VMs of resources but if there is not a huge amount of contention, yes one VM can use a larger amount of storage resources than others.
Bob