Update In a move likely timed to coincide with the opening of Oracle OpenWorld, VMware has made vSphere 5.5 available for download here - but the release of the latest version of its flagship product has been marred by the issuance of a warning to users of vSphere Replication 5.1 NOT to install 5.5.

vSphere Replication is a business continuity product that replicates virtual machines, usually so they can be stored in a second location for disaster recovery purposes. VMware likes to talk up its ability to copy only changed blocks in a virtual machine's .VMDK file, the better to save bandwidth.

The product is a module of VMware's lead virtualisation product, the vSphere hypervisor, and like its parent was recently upgraded to version 5.5.

But as explained in this knowledge-base article, “if you have Automatic Check and Install updates selected the vSphere Replication appliance will automatically upgrade to version 5.5”. If that happens on an existing vSphere 5.1 installation, very bad things will happen.

How bad? In a blog post, virtzilla warns “this will actually break your replication and is irreversible. It will require you to re-install VR 5.1 and redo your replications from scratch.”

Ouch.

VMware says the SNAFU was caused by “a mistake involving automated systems”.

The good news, if there is any in such a situation, is that the bad update emerged on a Friday. Those without automated updates installed may not have spent the weekend doing the upgrade and were forewarned. Those with automated installs enabled? VMware's blog says they should “please contact support for assistance.”

We'll leave it to you, dear readers, to decide whether to call a lawyer first.

Update

VMware has updated its original advisory to note that vCenter 5.5 is now available, If you install that upgrade, installing vSphere Replication 5.5 will no longer break anything.

The update also suggests users turn off the auto-update feature in vSphere Replication. ®