Hi and welcome to the communities,
vmkfstools -i SVR\ DS.vmdk -d thin Disk_1.vmdk...
Input/output error (327689)
Since you are doing the clone between two different datastores, can you confirm if both the datastores are of from same LUN or same local storage? The reason, i am asking is that I had seen this error once, when I was trying to clone a disk from a EMC array with powerpath plugins loaded to the local storage. But the error was gone after I did a rescan.
Again, can you do confirm on what the logs are saying about this,, vmkernel.log?