"write_lease: unable to write lease xxx.xxx.xxx.xxx" from dhcpd in Red Hat Enterprise Linux 6

Issue

• We have a dhcp failover configuration on 2 dhcpd machines.
• When both nodes of the dhcp failover is started, the the following error is output.

Mar 14 19:43:13 testserver dhcpd: Wrote 0 deleted host decls to leases file.
Mar 14 19:43:13 testserver dhcpd: Wrote 0 new dynamic host decls to leases file.
Mar 14 19:43:13 testserver dhcpd: write_lease: unable to write lease xxx.xxx.xxx.xxx

• We need to remove /var/lib/dhcpd/dhcpd.leases manually to avoid it and restart dhcpd. But, it's reproduced after a while.