“vmdk is larger than the maximum size supported by datastore”

[SnapDrive Error]: Please specify valid VMFS datastore name. (SnapDrive Error Code: 0xc0041033)

Have a read of this:

http://support.netapp.com/NOW/cgi-bin/bol?Type=Detail&Display=600206

Create a new vmfs5 datastore and then add the key listed in the article. No need to restart snapdrive. snapdrive will then use that as the file to back the RDM when it does a verification.