Resolving CommVault Simpana error code 91:29

Independent backup expert Brien Posey details what causes CommVault Simpana error 91:29 and how to resolve it in this Expert Answer.

What causes error code: 91:29 in CommVault Simpana and how can it be resolved?

Error 91:29 is one of the more frustrating errors that can occur with CommVault Simpana. The actual error text is:

Error Code: 91:29 -- Unable to Download the VMX File for Virtual Machine […].

In addition to the error message, you may see an error message stating: Expected put message got: error.

This error occurs in situations in which .VMX files are stored within a VMware data store that is shared by multiple hosts. Normally, an ESX host places a lock on .VMX files when a virtual machine is powered on, thereby causing access attempts from other hosts to fail.

This particular error (error code 91:29) only occurs under very specific circumstances. Specifically, it occurs when virtual machines are running Windows Server 2008 R2 Enterprise Edition on top of vSphere ESX 4.0. The problem occurs because the vCenter server is unable to determine which ESX host has locked the VMX file. If access is attempted from a host other than the one that has the lock on the file, then access will fail and an error message will be generated.

Although the error message specifically references the VMX files, CommVault documentation indicates that the problem can also occur as a result of a vCenter Server's inability to download .NVRAM files.

CommVault recommends that you solve this error by applying ESX 4.0 Update 2 or higher (you could also upgrade to a newer version of vSphere). As a last resort, you could create an identical set of credentials on each ESX host. For example, if your vCenter user is named CommVault, then you would need to create a user named CommVault on each one of your ESX servers. Keep in mind that the name CommVault is just an example. The name that you use should match your vCenter user name.

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