Troubleshooting

Enable Detailed Logging

If the current logs aren't enough to diagnose a backup failure, you can enable debug logging for more detailed information on the backup job.

To do this:

1. Manually start the backup job.

2. Then, select the "Log Level" option and change it from "Default" to "Debug."

3. Finally, click "Backup" to run the job.

Enabling CBT inside VMware vSphere

CBT is an optional feature for VMs and disks within VMware vSphere. To leverage CBT mode in Zmanda Pro, you'll need to enable CBT on the target VMs and their disks beforehand. Here's a simplified guide:

1. Power off the VM.

2. Access the VMware vSphere web interface and select "Edit" for the desired VM.

3. Go to the "VM Options" tab in the "Edit Settings" dialog box.

4. Locate the "General" section and find "Configuration Parameters." Click "Edit configuration."

5. Set ctkEnabled to TRUE to enable CBT or FALSE to disable it.

6. Repeat step 5 for each attached disk, setting scsix:x.ctkEnabled accordingly.

7. If disabling CBT, delete any *-CTK.VMDK files from the VM's directory using the datastore browser.

8. Power on the VM again.

Common errors and warnings

This section addresses frequently encountered errors and warnings you might experience during VM restore operations with Zmanda Pro. By understanding these messages, you can effectively troubleshoot potential issues and ensure successful recoveries.

CBT and Initial Backup:

• "No parent snapshot found. Fallback to full backup"

This message indicates that Zmanda Pro couldn't locate a suitable reference backup job for Changed Block Tracking (CBT). This typically happens during two scenarios:

1. First backup in a storage vault: When performing the initial backup within a new storage vault, there's no prior backup to reference for CBT. As a result, Zmanda Pro automatically defaults to a full backup. The subsequent backup, assuming success, should leverage CBT for increased efficiency.

2. Previous backup failure: If a previous backup attempt failed, Zmanda Pro might not be able to find a valid reference point for CBT. In this case, the current job will also proceed as a full backup. The next successful backup will then re-establish the CBT baseline and enable future CBT-based backups.

Snapshot Handling:

• "VM <name> contains <N> snapshots(s). Snapshots will be flattened during backup"

This message informs you that the target VM was running off a snapshot chain during the backup process. Zmanda Pro will create a flattened virtual disk image by merging the current snapshot with its parent(s) up to the base disk. This essentially consolidates the snapshot hierarchy into a single disk for the restored VM. While the snapshot tree structure won't be preserved, the current state of the VM will still be recovered.

Disk Changes and Inconsistencies:

• "Unable to run CBT: disk size changed <old> -> <new>"

This error signifies that the virtual disk size has changed since the last successful backup using CBT. As CBT relies on tracking block-level modifications, disk size alterations make it unusable. Zmanda Pro will automatically switch to a full back up in this scenario.

• "Unable to run CBT: inconsistent change id <old> -> <new>"

This message indicates that the change ID information for the virtual disk has become inconsistent compared to the last successful CBT backup. Inconsistent change IDs prevent Zmanda Pro from accurately identifying changed blocks. As a result, the current backup job will proceed as a full backup to ensure complete data capture.

Unsupported Disk Configurations:

• "Unsupported disk mode <mode>"

This error occurs when Zmanda Pro encounters a virtual disk configured with an unsupported independent disk mode (persistent or non-persistent). These disk modes don't support snapshots, which are a vital component of the Zmanda Pro backup process. Consequently, disks with such configurations will be skipped during the backup.

• "Unsupported disk backing"

This message indicates that Zmanda Pro encountered a virtual disk created using a format it doesn't recognize or support. Disks with unsupported backing formats will be skipped during the backup process.

Permission and Configuration Issues:

• "Error downloading file: download(<file URL>): 401 Unauthorized"

This error suggests that the credentials used lack the necessary "Datastore" role(s) on the target host or VM. To resolve this, ensure the credentials possess the appropriate permissions to access and download files from the relevant datastore and VM. Refer to the documentation for details on required roles and permissions.

• "CBT is not enabled on <vm name>"

This message highlights a configuration mismatch. While CBT might be enabled within the Zmanda Pro protected item settings, it's currently disabled on the target VM itself. To leverage CBT for backups, ensure CBT is activated on the target VM within VMware vSphere.

Informational Messages:

• "Disk chain before snapshot <list-of-vmdk>

• New snapshot file <list-of-vmdk>"

This message provides informative details about the virtual disk configuration associated with the VM. It lists the virtual disk chain before a snapshot is taken, followed by the newly created snapshot file. If there are multiple snapshot trees for the VM, this message will also display the specific chain being backed up.