Two region servers think that they own the same region: data loss

I observed this on a 100 node cluster that is constantly doing about 500K ops/second.

The region server on machine A was servicing IOs for a particular region. Then the machine went into a bad state where it is ping-able but not ssh-able. The master detected that there is a problem with machine A and reassigned the region to machine B. The regionserver on machine B opened the region and opened all the required HFiles for this region. After two hours, the NameNode received a delete request for one of the HFiles from machine A and happily renamed the file to HDFS-Trash. After another 3 hours or so, the regionserver on machine B tried to read contents from that HFile but failed because the file was renamed earlier. The region server on B in now stuck, and possible data loss.

The problems stems from the fact that although the master-and-ZK reassigned the region, the old regionserver was not possibly dead.