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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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