ALERT: Datto Drive Cloud service will no longer be available as of July 1, 2019. For more information, see our end-of-life article. If you'd like to migrate your data to Datto Workplace, see our migration guide.
To learn how to download your Datto Drive Cloud data, please visit this article.

Datto Windows Agent (DWA) 2.1: Software Release Notes



This article contains software release notes for Version 2.1 of the Datto Windows Agent.

For Version 2.0 and below, see our Datto Windows Agent (DWA) 1.0 & 2.0: Software Release Notes article.

For guidance about which Datto Windows Agent version is right for your protected system, review our Getting Started with the Datto Windows Agent article.


  • Datto Windows Agent Version 2.1



Release 2019-04-08

Agent Version


  • Enhanced the functionality of the agent paging file to allow Technical Support to optimize its performance in cases of very high and very low disk I/O
  • Added logic to allow the Datto Windows Agent to read the BIOS UUID of protected virtual systems as a component of the VMX backup process
  • Before allowing an update of existing agent software from Version 2.0 to Version 2.1, the Datto Windows Agent installer will require a reboot of the protected system if the host has major Windows updates pending

Vulnerability Fixes

  • Enable MercuryFTP target authentication

Bug Fixes

  • Resolved an issue which could cause the agent service to crash on /host call under low memory conditions
  • Corrected an issue which could cause backups to fail with an "err: 33" exit code
  • Fixed the agent version updater and reset legacy driver version bounds in version.xml
  • Excluded ValidateLocalTargets failures caused by SQLlite errors from the criteria for backup failure
  • Corrected an issue which prevented the /event API endpoint used by the SIRIS from functioning as expected
  • Resolved an issue which could cause a reboot prompt to surface on the protected machine when installing DWA Version over DWA Version

Release 2019-03-18

Agent Version 2.1 / Driver Version 1.12.11


  • AGENTS-449: This improvement introduces backup support for ReFS.
  • AGENTS-620: The Datto Windows Agent installer now uses MSI instead of NSIS.
  • AGENTS-877: This improvement enhances the Datto Windows Agent's ability to report services running on the production machine as a component of Advanced Backup Verification.
  • AGENTS-1274: 4K drives now back up as efficiently as non-4K drives.
  • AGENTS-335: With the release of this enhancement, Windows Update backup validation has been enhanced to avoid unnecessary differential merges.
  • AGENTS-359: A pending backup request will terminate if the Datto Windows Agent detects that status requests to the protected system from the Datto appliance have stopped.
  • AGENTS-360: With the release of Datto Windows Agent 2.1, support for NT 5 is deprecated.
  • AGENTS-425: This improvement introduces the ability to back up mounted volumes that are not mounted on a drive letter.
  • AGENTS-556: All binaries provided for the Datto Windows Agent include a Datto signature.
  • AGENTS-565: This enhancement introduces functionality into the agent driver which, when in incremental tracking mode, records the amount of data that has change and exposes it to an API.
  • AGENTS-591: This improvement allows the DattoBackupAgent service to start as a WiX component.
  • AGENTS-595, AGENTS-596, AGENTS-815, AGENTS-1022: These improvements introduce performance and UX enhancements to the Datto Windows Agent installer.
  • AGENTS-1019, AGENTS-1020: If a user installs the Datto Windows Agent on a protected system and does not reboot the machine after install, the agent can notify the Datto appliance of the need to reboot before backups can run successfully.
  • AGENTS-1031: This enhancement adds logic to the Datto Windows Agent which allows it to query a running driver and understand if it supports known features.

Vulnerability Fixes

  • AGENTS-437: Resolved an issue which could allow a restricted user system-level access to a protected machine via command-path injection.
  • AGENTS-1033: The Datto Windows Agent will only accept device connections using TLS 1.1 or above.
  • AGENTS-1148: This improvement disallows connections to be made to the Datto appliance from protected systems which use low or medium encryption cipher algorithms.
  • AGENTS-1383: Resolved an issue which caused the API key for CSR requests to display in plaintext.

Bug Fixes

  • AGENTS-362: Resolved an issue which could cause the iSCSI transport service to try to connect 25 times over 25 seconds for a connection failure on write.
  • AGENTS-589: Fixed the file search mechanism in WiX script for all versions of Windows to check the availability of driver files and dependency files.
  • AGENTS-393: Estimated size for full/diff incorrect
  • AGENTS-424: Agent update downloads are susceptible to MITM attacks
  • AGENTS-439: DWA with Win7/2008: CHKDSK (not read-only) fails with "Cannot open volume for direct access"
  • AGENTS-469: DWA BSODs: DattoFltr.sys with STOP 0x00000019 Bad_Pool_Header
  • AGENTS-480: Volume filter driver crashes with MAXIMUM_WAIT_OBJECTS_EXCEEDED when more than 64 volumes are mounted
  • AGENTS-484: Uninstaller fails to remove DattoCtrl/DattoSnap files from volumes with no drive letter
  • AGENTS-486: Not all mount points for volume are reported
  • AGENTS-504: DWA on large volumes (>1TB) has cow file sizes larger than 10GB
  • AGENTS-505: DattoFSF.sys driver info is incorrect
  • AGENTS-509: Copyrights are out of date
  • AGENTS-511: Uninstaller leaves behind "Datto" directory in app data
  • AGENTS-512: DattoSnapshot.exe says drivers not initialized
  • AGENTS-513: Increase filter communications port MaxConnections in DattoFSF filter driver
  • AGENTS-516: Service fails to start after the first install
  • AGENTS-522: Windows Firewall rules can be more specific
  • AGENTS-532: Agent update retry after failure occurs too frequently
  • AGENTS-538: Agent installer with identical driver versions installed sets reboot required
  • AGENTS-550: DWA backups cause Windows to play "New Hardware Detected," and Hardware Removed" sounds
  • AGENTS-575: Windows driver removed after major Windows upgrade
  • AGENTS-609: Offlining disk crashes the system
  • AGENTS-621: Update auto-update code to properly download and run new WiX installer
  • AGENTS-640: Backup failure not reported correctly
  • AGENTS-649: Windows bus driver file not removed and driver package left around after uninstall
  • AGENTS-665: Driver not loaded after Windows 10 Major Version upgrade
  • AGENTS-666: Full/diff backup types transfer size calculation is wrong if the file system is unsupported
  • AGENTS-718: DWA driver hangs if the snapshot device uninstalled unexpectedly
  • AGENTS-729: After a Windows update, 'Local System' account's local app data for the agent is not migrated.
  • AGENTS-756: Second instance of installer/uninstaller starts on x86
  • AGENTS-761: Agent installation failure if MSI installer is launched unelevated
  • AGENTS-765: Installer should fail if DattoFltrDriver fails to install
  • AGENTS-770: Windows volume filter driver file not removed and driver package left around after uninstall
  • AGENTS-775: Use compute32BitMaxBlockSize to find correct size incremental file
  • AGENTS-794: Incorrect parameters to POST /backup cause agent crash
  • AGENTS-813: Different version upgrades fail using just MSI
  • AGENTS-816: Event Viewer entries are not formatted correctly
  • AGENTS-817: WiX upgrades reboot unexpectedly
  • AGENTS-820: Second instance of uninstaller starts on x86
  • AGENTS-835: Migration of AppData after Windows Upgrade causes first agent startup to fail
  • AGENTS-843: %ProgramFiles%\Datto\Drivers folder not removed during uninstall after upgrade
  • AGENTS-845: WiX repair fail
  • AGENTS-887: Uninstall after upgrade does not remove files
  • AGENTS-892: MSI installer should implement rollback custom action(s)
  • AGENTS-896: Server 2008: Install fails if a newer version of vcredist installed
  • AGENTS-918: WiX upgrades with identical driver versions cause an unnecessary reboot
  • AGENTS-934: Possible small memory leak relating to curl and Certificate logic
  • AGENTS-936: BSOD on system restart after backup
  • AGENTS-939: Small memory leak for iSCSI backups after iSCSI target disconnect
  • AGENTS-954: DattoProvider not removed on uninstall
  • AGENTS-960: Prevent installation of DWA over DTC agent
  • AGENTS-964: connection_error is never set
  • AGENTS-965: DattoProvider registration is not working on Windows Legacy (XP/2k3)
  • AGENTS-969: Agents can fail with cow file size exceeded, but do not indicate a failure to the device
  • AGENTS-974: Agent does not close snapshot files after backup
  • AGENTS-978: DattoSnap not removed on uninstall
  • AGENTS-998: DattoFSF driver memory leak
  • AGENTS-1004: Event Viewer entries are not formatted correctly
  • AGENTS-1012: Install fails if a newer version of vcredist is already installed
  • AGENTS-1015: Failed install causes constant differential merges
  • AGENTS-1016: Event 55 NTFS errors
  • AGENTS-1028: Snapshot device should be opened with sharing mode and access rights as limited as possible
  • AGENTS-1029: Agent should not crash when running with old drivers
  • AGENTS-1036: DWA crashes if iSCSI is not available
  • AGENTS-1037: Agent version does not have patch/revision value
  • AGENTS-1044: Server 2019 reported as Server 2016
  • AGENTS-1045: Differential merge on latest DWA agent is a full when iSCSI transport is used
  • AGENTS-1054: Fix transport (iSCSI) class seek
  • AGENTS-1055: Windows fs parser doesn't work with ReFS.
  • AGENTS-1071: Windows driver roll-forward does not maintain changeset (2.1.X)
  • AGENTS-1075: Add VC redist check/search and bypass mechanism to MSI
  • AGENTS-1079: .datto.mif files left behind after uninstall
  • AGENTS-1082: Small memory leaks relating to curl and curl headers
  • AGENTS-1116: Unnecessary differential merge when a backup fails before snapshot mode
  • AGENTS-1123: VSS failure to prepare for backup causes unnecessary differential merge
  • AGENTS-1129: Potential BSOD while upgrading drivers to 1.12+ (SnapShim)
  • AGENTS-1139: ReFS: Large difference between bytesTransferred and totalSize
  • AGENTS-1151: 0-byte Dattoctl file created if insufficient space
  • AGENTS-1152: Failure to delete old log files should not fail backups
  • AGENTS-1160: Upgrade from legacy agent causes a full backup
  • AGENTS-1161: Installer UI InstallMessage text cut off on XP/2k3
  • AGENTS-1171: /v2/install API should report rebootRequired as true when drivers have been modified via upgrade or repair
  • AGENTS-1185: INF files are not valid for hardware signing
  • AGENTS-1199: DattoCtrl file is 10x larger than it should be for very large volumes
  • AGENTS-1208: Any exception throws within `compose*` would result in DWA/agent crash
  • AGENTS-1210: Confirm file replace file dialog should not appear while repair DWA
  • AGENTS-1211: Cannot backup after uninstalling agent and then installing again
  • AGENTS-1213: Win DriverInfoProvider does not query SnapShim driver
  • AGENTS-1220: Bus driver not installed on a fresh install (after an agent has been uninstalled)
  • AGENTS-1249: Some win32 API are failing on 4K driver on the snapshot volume
  • AGENTS-1283: Upgrades from 2.0.X to 2.1.X fail to install bus driver
  • AGENTS-1286: Upgrades from 2.0.X to 2.1.X always diff merge on Windows
  • AGENTS-1291: Agent is causing MercuryFTP to not close file handle for backup LUN
  • AGENTS-1346: Backups differential merges on upgrade ( ->
  • AGENTS-1356: Backup agent copies all blocks on huge 4K native drives
  • AGENTS-990: Constant differential merges on French OS
  • AGENTS-1289: Backup causes BSOD on Server 2019

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