had trouble making esxi4 see datastore of size 2TB. It is said this is max for a LUN only and could be bypassed by extents? how to do that?
Yeah, it's LVM-based so 2TB per extent, you can have up to 32 extents per datastore however, just open the datastore and add a second extent. Beware however that although v4 is better at dealing with extent-loss not killing the whole datastore it is still possible, it's not actually good practice to have particularly large datastores either, although it comes in handy every now and then.