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VMware 5.5 Enabling HA on a cluster fails around 60% with error "Cannot install the vCenter Server agent service. Unknown installer error System"


I just finished upgrading my hosts to ESXI 5.5

Now when I try to enable HA I get the following error.

Cannot install the vCenter Server agent service. Unknown installer error System
the kb articles tell me to reboot the hosts but that didn't fix anything.

If I show more details, I get the following information.
- Cannot upgrade vCenter agent on "HOST" in "STORAGE". Unknown installer error.
- The vSphere HA availability state of the host "HOST" in cluster in "NAME-HOST" in "STORAGE": vSphere HA agent cannot be correctly installed or configured

Let me know if you need any additional information.

1 Solution
Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
We've seen this possible issue many times, its maybe occurring because the ESXi OS installation is out of space.

When vCenter Server deploys thevHA agent to the host via a push it copies the tar ball to the host server and the servers partition must have space to receive the tar ball and then it extracts the tar ball which requires space and finally executes the package which requires space finally when HA agent is running communicates with other hosts and vCenter Server.

The answer will lie in the fdm.log on the host server as to the cause.
=To fix that you need to remove some software from bootbanks, OEM firmware updaters that never performed any function must be first to go.
TRTurnerAuthor Commented:
After updating to the ESXI hosts to the newest version. A quick reboot and everything started working.
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