VMware has released patch with build number 515841 of ESXi 5.0, to fix some errors.
Among them, this release fixes the problems with Storage UnMap iscsi commands; at the moment, the “brutal” solution has been made my completely disabling this feature. We hope for a future re-enablement when things will work as expected.
Among the other fixes, it’s interesting the ability to choose login timeout for iscsi initiators, obviously the software and dependent ones(independent are managed through the BIOS of the ethernet adapter).
For the complete fix list, have a look at this page.
At this link you can download this patch.