ESX does not support 2 terabyte LUN sizes

http://kb.vmware.com/kb/3371739
ESX does not support 2 terabyte LUN sizes

Workaround

Although the LUN size is limited to 2 terabytes - 512 bytes, the VMFS and datastore volume size limit is much greater. The maximum volume size is 64 terabytes - 16 kilobytes. This can be accomplished by leveraging the maximum extents per volume (which is 32).

If you require a single datastore which is larger than 2 terabytes - 512 bytes in size, you may want to add extents so that the datastore resides on multiple LUNs of 2 terabytes - 512 bytes or lower.