Avamar: Vmware Image Backup Issues on Windows VM with SQL Server

Summary: VMware image backups of Windows virtual machines running SQL Server may show inconsistent SQL log behavior when quiesce is enabled. In some scenarios, SQL logs record full database backups instead of COPY_ONLY events, which can disrupt existing backup chains. In other cases, SQL logs show no backup-related entries, indicating that the backup completed in a crash‑consistent state. These issues may be related to VMware Snapshot Provider settings, VSS configuration, or missing SQL VSS writers. ...

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Symptoms

Virtual Machine (VM) Image backup is taken with quiesce enabled (by default).

  • When VM image backup is taken for VM with SQL Server on it, we should see "DB Full (COPY_ONLY)" events in SQL Logs. Instead, we may have two different cases:
    1. Each Database gets "DB Full" backup created event in SQL logs
    2. There is no any 'backup' event at all registered on SQL.

Cause

Case 1:

  • By default, each image backup is using quiesce when creating a snapshot.
    • Relevant portion from backup log: 
      2018-05-01 22:01:02 avvcbimage Info <42650>: Creating snapshot 'Avamar-152521206017ff362a23f6a0cbf536c74c164886b6c56ad7b6', quiesceFS=1
.
.
.
2018-05-01 22:01:43 avvcbimage Info <42208>: No VSS manifest found. This is expected for non-Windows VMs, and older version of Windows VMs that do not support VSS.
2018-05-01 22:01:43 avvcbimage Info <42209>: For Windows VMs with VSS support, the VM must be powered on and VMware Tools must be running for the manifest file to be generated.
      In first case, the backup is application-consistent, however it does not create COPY_ONLY backups which can interfere (break backup chain) with other SQL backups on this SQL instance

Case 2:

  • We do not see "avvcbimage Info <42208> : No VSS manifest found" message in the image backup log, however there are no backup related events in SQL Log.
  • In second case, the backup is crash-consistent, so it does not capture all data and transactions in memory during the backup.

Resolution

Case 1:

  1. Check the state of "VMware Snapshot Provider" service.
  2. Ensure that the VMware Snapshot Provider is not running and that the startup type is listed as Manual.

Case 2:

  1. Check the writers list on affected SQL VM.
    1. As administrator in command prompt, run: vssadmin list writers
    2.  Ensure that SQL VSS Writer is listed,
      1. If not listed then address the issue to Windows/SQL Administrator if this writer is not present.
    3. For more info (both cases) check the KB below:
      Troubleshooting Volume Shadow Copy (VSS) quiesce related issues (External Link) 

Affected Products

Avamar Client

Products

Avamar Client
Article Properties
Article Number: 000031958
Article Type: Solution
Last Modified: 10 Mar 2026
Version:  4
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