VAAI got disabled during Storage vMotion and something about SIOC
At first, I got very poor performance when I was trying to svMotion a 20GB VM within the same Equallogic SAN between different volumes, it took over 20 minutes to complete, I thought there must be something wrong as I’ve already enabled VAAI.
After searching the net and discovered the problem is due to Different Block Size between the two volumes (1MB vs 2MB) that will actually disabled VAAI feature. 
So choosing the volumes with the same block size, I was able to reduce the time by almost 10 times!!!
See attached graph, 15:22 to 15:42 is the one without VAAI, 15:50 to 15:52 is the one with VAAI.
In additional, I have implemented Storage I/O Control today and found Storage vMotion with VAAI isn’t affected by SIOC as the whole svMotion is offloaded on to the EQL array, so SIOC won’t really kick in, you may say svMotion with VAAI is “Out of Control ”, this is another great thing about VAAI!
Finally, I do think SIOC is one of the best feature in ESX 4.1 for many cloud hosting providers as they can finally meet their storage SLA now besides the CPU and memory.
