How VAAI Helps Equallogic
I previously posted about the limits on iSCSI connections when using Equallogic arrays and MPIO. If you have lots of Datastores and lots of ESX hosts with multiple paths the numbers of connections multiplies pretty quickly. Now with VAAI support in the Equallogic 5.02 firmware (hopefully no recalls this time), the number of Virtual Machines per Datastore is not important. Among other improvements, the entire VMFS volume will not lock. As I understand VAAI the only the blocks (or files maybe?) are locked when exclusive access is needed.
Lets look at the improvement when using fewer larger EQ volumes: Old way (with 500GB Datastores for example): 8Hosts x 2(vmkernel connections) x 10(Datastores) = 160 connections (already too many for the smaller arrays, PS 4000).
VAAI (with 1.9 TB* Datastores) 8 Hosts x 2(vmkernel connections) x 3(Datastores) = 48 connections
The scalability for Equallogic is much better with VAAI when trying to stay under the connection limits.
_*Limit for VMFS is 2TB minus 512B so 1.9TB works out nicely. _