After a power failure or storage failure in a datacenter, TKC Nodes may go into a read-only state.
This can be confirmed by running a "touch /tmp/testfile" and it will fail with an "file-system in read only" error.
A fix was pushed in TKr's at or above 1.27.11 to detect and reboot nodes that are in this state.
On versions before this, the workaround is to ssh into the node and reboot it.