Sunday, February 5, 2017

Exchange Veeam Backup Timeout - VSSControl: Failed to prepare guest for freeze timeout 900 sec

We're using the Quest tool to migrate a ton of mailboxes from Notes over to Exchange, and since it uses quite a bit of resources on the Exchange servers, our Veeam backups were failing. This led to a massive amount of transaction logs building up in Exchange, which led to more backup failures. Round and round we went, never getting a good backup.

The error in Veeam was:

“VSSControl: Failed to prepare guest for freeze, wait timeout 900 sec."

The issue was that Veeam was timing out because it couldn't freeze the guest VM (the Exchange mailbox server) in order to start the backup. After the 900 seconds (15 minutes) expired, Veeam would give up and fail.

What I had to fix it was adjust a registry setting on the Veeam server, to lengthen the timeout threshold.

On the Veeam server, open regedit and navigate to:

HKEY_LOCAL_MACHINE\SOFTWARE\Veeam\Veeam Backup and Replication

Add a DWORD (32-bit) named VssPreparationTimeout

**Note** The value is in milliseconds (decimal), the default timeout is 900000, which equals 15 minutes

We're going to start by setting it to 30 minutes, so set the value to 1800000

**Note** Even after 30 minutes, mine kept failing so I had to keep bumping it up in increments until I found the sweetspot...which for me was 66 minutes.

After you create the DWORD, close regedit.

Stop any running jobs or wait for them to complete (which they won't), close the Veeam control panel, then restart the Veeam Backup Service.

Open the Veeam control panel up, and start your backup job.

Now it should freeze the guest successfully, and get a good backup!

1 comment:

  1. Performance settings to help with timeout errors can be adjusted through the proxy performance settings (Concurrent Threads, and limit network bandwidth). If you are still unable to get a Veeam Backup to azure due to these timeout errors after adjusting the Proxy Settings, you can contact Veeam Support to further fine-tune the settings.