I checked to see if VAAI is enabled on the ESXi5 hosts, and it is. I've verified that my IBM SVC running 6.2 code is HCL-good. But on the ESXi 4.0 U0 hosts, I don't see the 2 settings at all. Isn't the problem that VAAI is not for 4.0 but for 4.1 and later?
Regardless, I'm not starting to think that the problem is indeed with ESXi 5 hosts. For example, using the SVC, I cloned the production LUNs and presented them to just my 2 ESXi hosts. I tried rescanning the datastores, and it takes considerably longer when the SCSI reservations are in use. Rebooting the host, it takes longer to boot up when in use. So I think there is something similar going on with the ESXi5 hosts and iSCSI LUNs as there is with Fibre Channel LUNs.
