storage DRS vs vSAN

[epxert123]

hello, guys,

    I'm confusing Storage DRS with vSAN, from docs, it seems that Storage DRS is the similiar as VM DRS, which load-balances all your datastore IO/capacity.

    So can it provide HA for datastore?  I mean once a member in a 3-node-cluster(vSphpere HA and DRS enabled) fails, can all the VMs(VMDK is on Storage DRS)

    running on that host aren't affected.

    What's the difference between them?

[daphnissov]

The two technologies have nothing in common at all. Storage DRS (sDRS) is the same concept for storage as DRS is for compute. That is to say, existing, shared, external datastores can have their contents "balanced" among each other automatically taking into consideration space utilization and, optionally, latency. There is no redundancy or protection of that data that is spanned or replicated to any other members; if a datastore "dies" or becomes otherwise totally inaccessible to all hosts on which it is mounted, all VMs running there are also inaccessible. So sDRS is only a storage automation system whereas vSAN is an actual storage subsystem with file system, write semantics, distributed layout, etc.

[epxert123]

Thanks for your quick reply.

So can Storage DRS interoperate with Vmotion and vSphere HA?

In case of host fails,  the disks of VMs running on that host will automatically migrate to the other hosts?

If not, I'll use vSAN to make sure datastore high availability.

[daphnissov]

So can Storage DRS interoperate with Vmotion and vSphere HA?

sDRS can and does interoperation with vMotion and vSphere HA, but those are three different technologies right there.

In case of host fails,  the disks of VMs running on that host will automatically migrate to the other hosts?

This is a function of vSphere HA, and it's not that the "disks of VMs" migrate to other hosts, it's that the VM is restarted by other hosts. There is no movement of the VMs disks in that process.

If not, I'll use vSAN to make sure datastore high availability.

As I said, sDRS does not make datastores highly available. If you want a storage system with resiliency, then vSAN is what you should consider.

[TheBobkin]

Hello epxert123,

"I'm confusing Storage DRS with vSAN, from docs, it seems that Storage DRS is the similiar as VM DRS"

sDRS is a vSphere feature that manages migration of VM workloads between datastore as in the actual vmdks backing the VMs hard disks relocate, similarly to how DRS migrates VMs based on compute resources to other hosts to optimise the use of these resources. If backed by traditional SAN then these backing data may have no redundancy applied to them

"If not, I'll use vSAN to make sure datastore high availability."

vSAN is not just a vSphere feature that can be applied to any cluster, it is a converged storage-platform and thus it requires specific hardware (local disks and controllers), it doesn't require networked SAN storage and can make VMs highly available via redundant copies of VM data distributed across the cluster of hosts.

HA can be used in conjunction with vSAN to restart VMs on isolated or failed hosts, DRS can be used to automate or advise on VM migration to under utilised hosts from a compute perspective.

Bob

[epxert123]

Thank you all a lot, it helps a lot and clears my confusion.