KVM guest system freezes during live migration RHEL 6

Issue

Virtual machine freezes after a live migration while accessing the hard disk. I have 2 RHEL6 hosts and want to migrate a RHEL6 (KVM) guest from one host to the other. This migration fails when running a command like the following on the virtual machine:
```
  while [[ "1" == "1" ]]; do echo "$1" >> /tmp/abc.txt; i=$(expr $i + 1);done
```
The root hard disk is mounted using NFS with the following options
```
  /exports/virtimages *(rw,no_root_squash,async)
```
Without writing to the harddisk the migration works.

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