Duplicate VSS Snapshots with Equalogic Automatic Snapshot Manager (ASM) and AppAssure (4037611)

Duplicate VSS Snapshots with Equalogic Automatic Snapshot Manager (ASM) and AppAssure

Backup errors can be experienced with either Automatic Snapshot Manager (ASM) which is part of the Equalogic Hit Kit or with AppAssure when VSS snapshots are scheduled at the same time.  ASM coordinates the creation, recovery and scheduling of VSS-compliant EqualLogic SANbased snapshots of Hyper-V and VMware virtual machines helping enhance protection, storage utilization, and performance. ASM integrates with Microsoft Volume Shadow Copy Services (VSS) framework providing application-consistent snapshots.

AppAssure also uses Microsoft Volume Shadow Copy Service to provide volume level application-consistent snapshots for point in time data restore

When two different services try to take a Volume Shadow Copy Service (VSS) snapshot of the same volume at the same time, snapshot conflicts may occur.  Specifically, whichever VSS request occurs second may fail and then retry based on whatever retry logic is built in.  AppAssure snapshots do have retry logic available and it is important to note that the default retry count is set to 0.

Solution 1:

Schedule ASM and AppAssure to not overlap when processing a VSS shadow copy request.  This allows VSS to process volume-level snapshots for both services without conflicts. Because of the queuing nature of AppAssure backups, it can be difficult to implement this solution because the time that the AppAssure backup actually launches can be hard to predict.

Solution 2:

Increase the number of AppAssure snapshot retrys.  Should ASM be in the middle of taking a snapshot, increasing the number of AppAssure snapshot retrys may be able to capture a recovery point without waiting for the next snapshot interval to take place.  To increase the number of AppAssure retrys, complete the following steps:

• Open the WebUI
• Click on the Configuration Tab
• Select Settings in the left-hand list
• In the 'Transfer Queue" section, click the "Change" button
• Set Maximum Retries to 3

It is important to note that each retry job can still fail with ASM running for extended periods of time. AppAssure will track each failed job attempt and alert you via email if you have enabled that feature.  You may also need to increase the retry count to 6 or more if you chose this solution.

In some instances where the backup schedules for both ASM and AppAssure are spaced apart, the ASM VSS snapshot may still exist causing all subsequent AppAssure  VSS backups to fail.  You may need to manually remove any remove persistent shadow copies left over by ASM that can hamper the success of AppAssure's backups.  For detailed instructions on removing persistent shadow copies, please review KB Article 137398.