I have faced this same problem in my lab few days back. Hit this forum post & found no resolution so saved it so I can post the resolution when I find it.
That seems to normally happen if your LUN has some file system that it can not understand or modify. Previous to vSphere 5.x you were to use fdisk to fix it in 5.x & above you would use PartedUtil. You can all find more details on this at: http://www.virtualizationteam.com/virtualization-vmware/vsphere-virtualization-vmware/call-hostdatastoresystem-createvmfsdatastore-for-object-ha-datastoresystem-on-esxi-xxx-xxx-xxx-xxx-failed.html
Hope this help!
Regards,
Eiad Al-Aqqad