Backup Exec 16 workaround for backing up size exceptions when using virtual machine to incrementally back up SQL

Before the customer made a be backup project, in which there is a case, there is a SQL virtual confidential backup, 1 full-time weekly, one increment per day, the GRT opened.

After doing the backup test, the first full preparation of the success, no exception, the data is 200G, the next day to make an increment when the situation, the size of the incremental backup is 800G, but the backup is successful, no error, no exception.

In the absence of a third-party backup of SQL, other snapshot presence, and agent problems, the size of the increment is still 800G. After viewing the virtual machine parameters, found that the client's virtual machine does not have the parameters of the CBT, so added in the virtual machine after adding the CBT parameters for incremental backup, backup size normal, problem resolution.

The so-called CBT refers to a virtual machine running on a Esx/esxi host that can track changed disk sectors. This feature is known as block Modification Tracking (CBT). On many file systems, CBT identifies the modified disk sector between the two changeset IDs. On a VMFS partition, CBT can also identify all the disk sectors that are in use. Block modifications to virtual disks can be tracked from outside the virtual machine in the virtualization layer. When the software performs a backup, it can request that only data blocks that have changed since the last backup or data blocks being used be transferred. The CBT feature is part of VSphere APIs for Data Protection (VADP), and third-party applications can access this feature. By calling VADP, an application can request VMkernel to return a block of data that has changed on the virtual disk since the last backup snapshot.

To enable CBT on a virtual machine, do the following:

1. Turn off the virtual electromechanical source.

2. Right-click the virtual machine, and then click Edit Settings.

3. Click the Options tab.

4. Click General under the Advanced area, and then click Configuration Parameters. The Configure Parameters dialog box opens.

5. Click Add Row.

6. Add the ctkenabled parameter, and then set its value to true.

7. Click Add Row, add scsi0:0.ctkenabled, and then set its value to true. Note: The scsi0:0 in scsi0:0.ctkenabled Indicates that the SCSI device is assigned to the hard disk that is added to the virtual machine. A SCSI device is provided to each hard disk that is added to the virtual machine, as shown in scsi0:0, scsi0:1, or SCSI 1:1. CBT is enabled (or disabled) on each disk, respectively.

8. Open the virtual electromechanical source.
   

9. In the home directory of the virtual machine, verify that each disk that has CBT enabled also has a VMNAME-CTK.VMDK file.

Backup Exec 16 workaround for backing up size exceptions when using virtual machine to incrementally back up SQL