Error 0x800F0A1 when installing Windows Server 2008 R2 SP1 on a Veeam Backup & Replication server

You might encounter an issue during the installation of SP1 for Win7/R2 where the installer exits with: 0x800f0a12. According to this and this article the solution is to enable automount.

If Veeam is using Direct SAN Access you do not want to enable automount without taken some steps. By Automount enable setting Windows will re-signature the VMFS volume which will lead to the volume not being recognised as a datastore by the ESX hosts. If you ever get in a situation like that read at how to resolve the issue.

To install SP1, follow the instructions below. They are taken from a recent thread the Veeam forum.

 Procedure to install SP1: (Drive J can be any free drive letter not used).

1. At command promtp: Type “mountvol /? “(This will display help and will also list volumes). Identify system partition (will not have drive letter) ie: \\?\Volume{9be074ce-d55f-11df-83d7-806e6f6e6963}
2. Mount a temporary drive letter to the system partion “mountvol j:/ \\?\Volume{9be074ce-d55f-11df-83d7-806e6f6e6963}” (Enter your own system partition guid).
3. Run SP 1 update and restart.
4. Dismount temporary drive “mountvol j: /d”.

An alternative approach would be remove the iSCSI or FC cabling or remove the Veeam host from the access list in the fabric.

The most time consuming option would be this:

1. Disconnect all active iSCSI connections and REMOVE the Target Portal from iSCSI favourite tab.

2. From command prompt, issue the followings:
> diskpart
> automount enable

3. Reboot the server then go ahead and upgrade your W2K8 R2 with SP1, it will take about 50 minutes to complete, yes, it did take that long even on latest powerful server.

4. Then issue the following AFTER reboot:
> diskpart
> automount disable

5. Reboot the last time and then re-establish all previous iSCSI connections as usual.


About Marcel van den Berg
I am a technical consultant with a strong focus on server virtualization, desktop virtualization, cloud computing and business continuity/disaster recovery.

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