Optimized message retransmission mechanism for distributed storage virtualization directory system

A non-transitory machine readable medium storing a program for retransmitting a multicast message through a unicast channel in a virtual distributed storage system comprising a cluster of nodes comprising a master node and a set of agent nodes, each node in the cluster of nodes maintaining a copy of a directory of the virtual distributed storage system, the master node multicasting messages to the agent nodes through a multicast channel to update the directory, the program executable by a set of processing units of the master node, the program comprising sets of instructions for:

• determining that a particular message to update the directory exceeds a maximum size limit for transmission to the agent nodes through the multicast channel, the particular message comprising an identification of the message;
• multicasting a retransmission trigger message from the master node to each of the agent nodes, the retransmission trigger message comprising the identification of the particular message, wherein the master and the agent nodes utilize a protocol to communicate the multicast and unicast messages, wherein said protocol does not allow the master node to send an unsolicited unicast message to an agent node;
• receiving, in response to the retransmission trigger message, a retransmission request message at the master node from each of the agent nodes through a unicast channel established between the master node and the agent node;
• and
• sending, in response to the receiving of the retransmission request message from each agent node, the particular message to update the directory from the master node to the agent node through the unicast channel established between the master node and the agent node.