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This article describes an update to improve the Microsoft Azure Backup performance. Before you install this update, see the Prerequisites section. Additional steps for configuration are required to enable this update after the installation.


The incremental backups by using the Azure Backup agent may run slowly for servers that have many files.


To fix this problem, install the latest version of the Microsoft Azure Recovery Services agent.

Additionally, add a registry entry that's described in the "Registry information" section, and follow the instructions in the "Increase default size of USN journal" section to increase the default size of the USN journal in the volumes that are being protected.

Download Center

The following file is available for download from the Microsoft Download Center:

Download Download the Azure Recovery Services agent update now.
Note The latest version of the Microsoft Azure Recovery Services agent is 2.0.8724.0.

Update information


To apply this update, you must have Azure Backup agent installed.

Restart information

You may have to restart the computer after you apply this update.

Replacement information

This update replaces the previously released update 3080243.

Additional configuration steps

Registry information

After you install this update, you must add the following registry entry.

Important Follow the steps in this section carefully. Serious problems might occur if you modify the registry incorrectly. Before you modify it, back up the registry for restorationin case problems occur.

  1. In Registry Editor, locate and then select the following registry subkey:

    HKEY_LOCAL_MACHINE\Software\Microsoft\Windows Azure Backup\Config\CloudBackupProvider

  2. Press and hold (or right-click) CloudBackupProvider, point to New, and then click DWORD (32-bit) Value.

  3. Name the new registry entry as UseUsnIterator.

  4. Double-click the UseUsnIterator registry entry.

  5. In the Edit DWORD Value dialog box, enter 1 in the Value data field, and then click OK.

  6. Exit Registry Editor.

Note To turn off the performance fixes, set the values to 0.

The new registry entry should resemble the entry in the following screen shot.

The screen shot of the registry entry

Increase default size of USN journal

The performance fixes that are provided in this update use the USN Journal in Windows. By default, Windows allocates only a small amount of space for the USN Journal. We recommend that you increase the default space that is allocated for the USN Journal based on the number of files that are being protected.

To check the current value that is set for USN, run the following command at an elevated command prompt:

fsutil usn queryjournal C: 

The command output resembles the following screen shot:

The hex value for "Maximum Size" (0x000000000200000) indicates that the current space that's allocated for the USN Journal is 2 MB.

You can increase the space that is allocated for the USN Journal by setting the Maximum Size and the Allocation Delta. The allocation delta is typically one-eighth of the Maximum Size.

Run the following command at an elevated command prompt:

fsutil usn createjournal m=67108864 a=8388608 C: Note Run this command for all volumes that are being protected.

The following table contains the values to be set, based on the number of files that are being protected. 


Maximum Size (m) in bytes

Allocation Delta (a) in bytes

1 000 000

1 342 177 280

167 772 160

1 200 000

1 610 612 736

201 326 592

1 600 000

2 147 483 648

268 435 456

2 000 000

2 684 354 560

335 544 320

2 400 000

3 221 225 472

402 653 184

2 800 000

3 758 096 384

469 762 048

3 200 000

4 294 967 296

536 870 912


Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.


Learn about the terminology that Microsoft uses to describe software updates.

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