Vcenter 5.1 and V400 3par -- where does VAAI really help?

[mujzeptu]

I am curious about when/where VAAI really helps?

Below I have 3 scenarios, all of them assume a cluster has shared storage between itself but no shared storage between clusters.

Scenario 1:

You want to vmotion a vm in Cluster A from one ClusterA-Storage1 to ClusterA-Storage2 datastore. What is VAAI doing if anything?

Scenario 2:

You want to move an offline vm from Cluster A to Cluster B. Is VAAI used at all? Is this just using the management network to migrate the data and less of the SAN?

Scenario 3:

You want to create new vms from a template. You kick off clone jobs. The tempate sits in Cluster A and you are creating a clone also in Cluster A, but also Cluster B and Cluster C. Does this use VAAI at all? Does it just use it in Cluster A?

We are trying to determine where VAAI is truly putting the work on the array itself and where it is all just being processed by ESXi, and in turn, just stressing out the management network to move this data.

[Richard Siemers]

Its my understanding that:

1) should offload the copy to the storage.
2) No vaai used, copy is over network.
3) Just Cluster A. You might be able to do something fancy with a dedicated template datastore shared to all clusters.

[hdtvguy]

I understand the theory, but have been meaning to try and find a way to prove what benefit it has, or even if it is really being used as several vendors have had implementation issues. I still find storage migration tasks painfully slow.

[Richard Siemers]

I would suggest as an audit to this functionality to monitor the bandwidth from the host to the storage through the switch. This should give you an idea of the impact of the VAAI offloading.

If you're having bottleneck issues at the host CPU-HBA/SAN switch/ISL links/Storage Front End Ports and not at the backend storage, offloading should be a benefit. If the bottle neck is the backend storage, then I would not expect much performance gain.

[yizhar]

Hi.

Please note that you can quite easily test this by enabling and disabling VAAI, comparing bottom line results of different actions.

VMware KB Disabling the VAAI functionality in ESXi-ESX
http://kb.vmware.com/selfservice/micros ... Id=1033665