There’s a new problem a few customers have reported whereby-

  • ESX disconnects randomly from VirtualCenter
  • ESX disconnects when performing VI Client tasks from VirtualCenter.
  • Tasks randomly timeout after a long idle time
  • “An error occurred communicating to the remote host” pops up.

This only refers to Update 3. This issue seem to be affecting customers with firewalls using state-ful inspection, such as a Juniper ISG 2000, Software Revision 6.1.0R3.

The problem occurs because of SOAP timeouts, and this behavior did not exist in VC 2.0.x or 2.5 GA, as they used a different mechanism to communicate with ESX.

A knowledgebase article is in the works, but Engineering is still actively investigating this problem. One work-around that I have seen mentioned (not verified to work!) is as follows:

  • Create a dummy VM on each host (e.g. 16 MB RAM, no disk, no network).
  • Set CPU affinity to the last core to prevent VMotion.
  • Create a new Scheduled Task that performs:
    • Change power state: Power-on dummy VM. Every hour, on the hour.
  • Create another Scheduled Task that performs:
    • Change power state: Power-off dummy VM. Every hour, 30 minutes after the hour.

Like I said, Engineering is aware of this issue and actively investigating it.