The incremental image fails to mount

Summary

If the backup disk is removable, mounting an incremental image might fail. 

– Microsoft iscsi software target
– USB HDD
– Shared disk type cluster (MSCS, MSFC)

Failure scenarios

Environment:
– Disk connected by iSCSI: X drive
– Backup Target Drive: X drive

– Node A: ActiveImage Protector installed.
– Node B: ActiveImage Protector not installed

Steps:
1) Node A: Performs basic and incremental backup.
2) Node A: Disconnect the X drive.
3) Node B: Connect X drive.
4) Node B: Update data in X drive.
5) Node B: Disconnect the X drive.
6) Node A: Connect X drive.
7) Node A: Perform incremental backup.
Currently, ActiveImage Protector updates the $AIPMAP of the X drive. However, because the machine ID remains the same, incremental backups should work correctly.

The following error occurs when you mount an incremental image that was created in step 7):

X: (allocated drive letter) cannot be accessed.
A file or directory is corrupted and unreadable.

Even if mounting an image succeeds, the newly added or pre-existing data may not be accurate. 

Cause

ActiveImage Protector creates a $AIPMAP file to track bitmap information, which includes the machine ID. However, it cannot track data changes made by other servers. As a result, it creates incremental backups based on changes made by the other server, leading to inconsistencies between the actual data and the incremental image file.

Workaround

1) Turning off and on the schedule will prompt a reconciliation during the next incremental backup.
2) Perform a basic backup.

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