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First things first

Clone this repository with

git clone --recursive <url>

else you get an incomplete checkout.

If you need installable binaries with a signed driver please go to

If you need support, please contact Linbit ( at

What is WinDRBD?

WinDRBD is a port of Linbit's Distributed Replicated Block Device Linux driver to Microsoft Windows. Technically it is a thin compatibility layer that maps Linux specific kernel API calls to the Microsoft Windows NT Kernel API.

DRBD itself is used to build High Availability clusters by replicating contents of block devices over a network to (up to 31) other nodes.

WinDRBD is based on DRBD 9. It was originally started by Korean company Mantech and was later rewritten by Johannes Thoma for Linbit.

DRBD devices are exported as SCSI disks as soon as the resource becomes primary and can be partitioned and formatted with the standard Windows tools (diskpart, partition editor in control panel, powershell).

What else is needed?

If you have a binary package, you don't need to install CygWin since the Cygwin DLL comes with the binary package. Commands like drbdadm and windrbd should work out-of-the-box with the Windows cmd shell.

We strongly recommend to use the binary packages provided by Linbit since they are signed with a Microsoft key and therefore should load without putting Windows into test mode.

For detailed build instructions, please see the file INSTALL. Having said that you need a Windows box with CygWin installed and a Linux box to build WinDRBD from source.

For building you need Ewdk from Microsoft and a separate Linux Box with spatch (concinelle) installed.

You need a recent version of drbd-utils. To obtain it, do a:

git clone --recursive

and follow the build instruction in file of the repo.

Configuring DRBD

The DRBD config files can be found in following folder:


The C:\windrbd folder can be configured at installation time (use this for example if your C: drive is read only).

Put your resources (extension .res) into the C:\windrbd\etc\drbd.d folder (from within a CygWin shell you can access this via


Then with

drbdadm up <name>

you can bring your DRBD resource up. Please refer to the DRBD Users guide (be sure to pick the 9.0 version) for more information of how to configure and administrate DRBD. Most drbdadm commands should work exactly like with the Linux version of DRBD.

Note that since WinDRBD and DRBD are very similar many procedures from the DRBD user's guide should also work with WinDRBD. Currently there is no separate WinDRBD user's guide.

There is also a WinDRBD specific tech guide which explains how to prepare two Windows Server 2016 nodes for use with WinDRBD. Please see the Linbit website for that guide.

Also there are some newer (beginning 2023) articles on

Differences to Linux DRBD

Note that there is a more detailed documentation of the differences on

In the configuration the only difference to Linux DRBD is that block devices are specified as you would expect it under Microsoft Windows, that is drive letters or GUID's are used. Examples:

disk "F:";
# or:
disk "0b098289-8295-11e7-bddb-0800274272c4";

We recommend not to assign drive letters to backing devices, since that easily may confuse the user. You can use the mountvol utility to find the GUID of a device.

Disk devices present themselves as a regular SCSI disk (like a physical hard disk) and appear as disk in the Windows partition manager (and also in device manager). With partition manager a partition table can be created and then partitions (with assigned drive letters) can be created on the disk. The partitions can be formatted with all supported file systems. This means that that normally there is be a partition table on the disk (under Linux, kpartx can be used to create device nodes for each partition).

Example for a disk device would be:

device minor 42;

(with no mount point). Mount points can be assigned with partition manager.

A special case of the disk device is the boot device. Booting from a remote (Linux) server is possible now (however without local backing storage and installation is quite difficult now). There is a document on

("Setting up WinDRBD diskless boot") that describes the process (which is subject to change).

Current limitations

The current 1.1 branch has following restrictions:

  • Auto-promote is not supported.

  • No read access when there are only secondaries.

  • For booting via WinDRBD the installation onto a WinDRBD volume is not possible yet with the Windows installer GUI.

  • Currently no 32-Bit version is supported, only 64 bit.


To view the log file go to


If you need remote logging, please read on.

We use syslog UDP packets and a Linux host to debug WinDRBD.

To configure the log host set a Registry key (string value):


and assign it the IP address.

You can use

windrbd set-syslog-ip ipv4-address

to change the syslog IP for this session (the registry key is only evaluated at server start).

If you are logging to the local Windows machine, use as IP address (this is the default).

There is also a logfile written by the installer located in the %TEMP% directory. It should be consulted when something with the installation goes wrong.

Version history

  • 0.1 (Oct 25, 2017): Basic I/O works with separate DRBD device.
  • 0.2 (Nov 13, 2017): Creation and basic usage of NT filesystem on DRBD device works.
  • 0.2.1 (Nov 16, 2017): Patch bootsector to hide NTFS on backing device from NTFS driver.
  • 0.3.0 (Dec 20, 2017): Connection from windrbd to Linux DRBD works.
  • 0.3.1 (Dec 20, 2017): Fixed a blue screen introduced with 0.3.0
  • 0.3.2 (Dec 21, 2017): Implemented device open and close methods.
  • 0.3.3 (Dec 26, 2017): Connection from Linux DRBD to windrbd also works.
  • 0.3.4 (Jan 05, 2018): Fixed several blue screens.
  • 0.3.5 (Jan 09, 2018): Fixed additional blue screen when connected.
  • 0.3.6 (Jan 09, 2018): Updated version of DRBD this is based on.
  • 0.3.7 (Jan 11, 2018): Local I/O works again.
  • 0.4.0 (Jan 12, 2018): Removed lots of legacy code.
  • 0.4.1 (Jan 19, 2018): Sync is almost working.
  • 0.4.2 (Jan 22, 2018): Support for I/O to/from backing device with more than 32 pages (needed to split requests).
  • 0.4.3 (Jan 26, 2018): Fixed a blue screen.
  • 0.4.4 (Jan 27, 2018): Fixed a blue screen on system shutdown.
  • 0.4.5 (Jan 29, 2018): Fixed a data integrity error on sync
  • 0.4.6 (Feb 06, 2018): supend-io and resume-io should work (quorum not)
  • 0.4.7 (Feb 07, 2018): Fixed a Windows 10 blue screen when accessing the windrbd device.
  • 0.4.8 (Feb 15, 2018): Refuse to attach to a backing device containing a (known) file system.
  • 0.4.9 (Feb 16, 2018): Fixed a blue screen introduced in last commit.
  • 0.5.0 (Feb 27, 2018): Beta 1
  • 0.5.1 (Mar 14, 2018): Implemented flushing in windrbd device.
  • 0.5.2 (Mar 20, 2018): Auto-hide filesystem on attach (user space changes only).
  • 0.5.3 (Mar 28, 2018): Assign drive letter from drbd.conf
  • 0.5.4 (Mar 28, 2018): Fixed blue screen on drbdadm down and no mount point.
  • 0.6.0 (Mar 29, 2018): Beta 2: Usability improvements.
  • 0.6.1 (Apr 17, 2018): Use Mountmanager to create Symlinks.
  • 0.6.2 (Apr 17, 2018): Fixed reference count error on drbdadm down introduced with last release.
  • 0.6.3 (Apr 24, 2018): Fixed blue screen on writing while connected.
  • 0.6.4 (May 08, 2018): Fixed very slow sync performance problem (and upgraded to DRBD 9.0.13).
  • 0.6.5 (May 09, 2018): Fixed memleaks introduced with last release.
  • 0.6.6 (May 11, 2018): Upgraded to DRBD 9.0.14, solving broken split brain handling.
  • 0.6.7 (May 14, 2018): Fixed pachting bootsector. Patch is not propagated to peers.
  • 0.7.0 (May 15, 2018): Beta 3: Stability fixes
  • 0.7.1 (May 24, 2018): Notify Windows explorer about new disk drive(s) (user space only)
  • 0.7.2 (May 28, 2018): Windows device only exists while primary.
  • 0.7.3 (Jun 15, 2018): Networking fixes
  • 0.7.4 (Jun 19, 2018): Error handling on backing device (with fault injection)
  • 0.8.0 (Jul 06, 2018): Beta 4: First public beta
  • 0.8.1 (Jul 10, 2018): Handling unplugging USB stick should work now.
  • 0.8.2 (Jul 31, 2018): Split WinDRBD requests into 1Meg pieces for DRBD
  • 0.8.3 (Aug 01, 2018): Fixed BSOD requests > 1Meg and backing dev failure.
  • 0.8.4 (Aug 02, 2018): Performance: do not split into 4K requests.
  • 0.8.5 (Aug 15, 2018): Fault injection framework, fixed permissions
  • 0.8.6 (Aug 27, 2018): Kernel interface now based on ioctl() instead of TCP/IP
  • 0.8.7 (Sep 03, 2018): User mode helpers, do not load driver on boot
  • 0.8.8 (Sep 17, 2018): kmalloc() debugger. For driver unload to work someday.
  • 0.8.9 (Sep 27, 2018): Uninstall works (but needs reboot), switched to inno-setup for installation.
  • 0.8.10 (Oct 10,2018): Autostarting user mode helper and log server as Windows Services.
  • 0.8.11 (Oct 12,2018): Report kernel driver versions over ioctl's
  • 0.8.12 (Oct 17,2018): Upgraded DRBD to 9.0.15
  • 0.8.13 (Oct 30,2018): Fixed memory leak in I/O path
  • 0.8.14 (Nov 02,2018): Upgraded DRBD to 9.0.16
  • 0.8.15 (Nov 13,2018): Sendbuffer limit, fixed BSOD on I/O while connected
  • 0.8.16 (Nov 14,2018): Some last fixes to installer
  • 0.8.17 (Nov 16,2018): Fixed sync stall bug
  • 0.8.18 (Nov 21,2018): Disallow driver unload when there are resources up
  • 0.8.19 (Nov 29,2018): Tech guide
  • 0.9.0 (Dec 03, 2018): Public beta
  • 0.9.1 (Dec 04, 2018): Fixed a buffer overflow in user space utility
  • 0.9.2 (Apr 10, 2019): DRBD 9.0.17, support for n > 2 nodes
  • 0.10.0 (Oct 15, 2019): Use WinDRBD device as system root ("C:") (without local backing storage and in VMs only).
  • 0.10.1 (Nov 6, 2019): Data devices and Disk devices work again.
  • 0.10.2 (Nov 14,2019): iPXE passes network address to kernel: no need for static IP and StartType registry patch for booting.
  • 0.10.3 (Nov 18,2019): Fixed logging (IP address was hardcoded)
  • 0.10.4 (Jan 31,2020): Stability fixes
  • 0.10.5 (Mar 03,2020): Key/Value based boot config
  • 0.10.6 (Apr 1, 2020): Upgraded DRBD to 9.0.22
  • 0.10.7 (May 6, 2020): Online verify, drbdadm status as non-admin and other useful mini-features (see
  • 1.0.0-rc1 (Jul 3, 2020): Stability fixes
  • 1.0.0-rc2 (Jul 30, 2020): Fixed fio BSOD
  • 1.0.0-rc3 (Aug 4, 2020): Fixed BSOD on upgrade
  • 1.0.0-rc4 (Aug 5, 2020): Fixed boot failure introduced with 1.0.0-rc2
  • 1.0.0-rc5 (Sep 14, 2020): Reengineered workqueues, stability fixes.
  • 1.0.0-rc6 (Oct 8, 2020): Fixed workqueues and ko-count mechanism
  • 1.0.0-rc7 (Oct 14, 2020): Upgrade to DRBD 9.0.25
  • 1.0.0-rc8 (Nov 6, 2020): Fixed many lockups, fixed 2TB limit
  • 1.0.0-rc9 (Dec 11, 2020): Optimized SyncTarget, many fixes when becoming secondary and fixed BSOD on disconnect while sync
  • 1.0.0-rc10 (Feb 24, 2021): Optimized secondary writes, fixed wait_event and completions (they should be non-interruptible)
  • 1.0.0-rc11 (Apr 26, 2021): Upgrade to DRBD 9.0.28, Fixed mod_timer causing system hang on disconnect
  • 1.0.0-rc12 (May 17, 2021): Fixed 3 stability issues, drbd utils support relocation. Now ran 5 days in disconnect/connect loop without issues.
  • 1.0.0-rc13 (Aug 2, 2021): Upgrade to DRBD 9.0.29, fixed most issues found by driver verifier.
  • 1.0.0-rc14 (Sep 14, 2021): Event log, config key, bundle sed and bash
  • 1.0.0-rc15 (Sep 23, 2021): Installer prompts for install paths.
  • 1.0.0-rc16 (Sep 30, 2021): Fixed a bug that caused volumes with size 1-2 TB not to work properly.
  • 1.0.0-rc17 (Oct 22, 2021): Online resize, no reboot on upgrade/uninstall and many other improvements (see
  • 1.0.0-rc18 (Nov 5, 2021): Installer and event log BSOD fixes
  • 1.0.0-rc19 (Jan 12, 2022): Fixed sync BSOD and hard network shutdown BSOD
  • 1.0.0-rc20 (Jan 25, 2022): Upgrade to DRBD 9.0.32, Fixed invalid page chain bug and some memory leaks.
  • 1.0.0-rc21 (Feb 3, 2022): Do not generate a new current UUID while IO is frozen
  • 1.0.0 (Feb 4, 2022): Production ready release.
  • 1.0.1 (Feb 17, 2022): No timeout for user mode helpers, minor JSON fix
  • 1.0.2 (Mar 28, 2022): Do not fill log file when drbdadm status is run periodically.
  • 1.1.0-rc1 (May 20, 2022): Secure boot, fix most HLK test failures, updated cygwin binaries
  • 1.1.0-rc2 (Aug 17, 2022): Some fixes, improve sync source speed
  • 1.1.0-rc3 (Sep 9, 2022): Fixed c-max-rate, negotiating stuckness, existing NTFS data
  • 1.1.0-rc4 (Sep 27, 2022): Quit drbdsetup events2 on driver unload, fixed remove lock BSOD
  • 1.1.0-rc5 (Oct 19, 2022): drbdadm adjust does not detach, drbdsetup hang fix
  • 1.1.0 (Oct 25, 2022): SecureBoot support, many smaller fixes
  • 1.1.1 (Oct 28, 2022): Release for upgrading from 1.1.0 without official signature
  • 1.1.2 (Nov 3, 2022): Fixed a BSOD when REMOVE_DEVICE timed out
  • 1.1.3 (Nov 11, 2022): Show driver unload messages, fix BSOD on unsuccessful driver update
  • 1.1.4-rc1 (Dec 7, 2022): Virtual partition table for existing NTFS data partitions
  • 1.1.4 (Jan 23, 2023): Drive letter in config ignored, fixed a memory leak, virtual partition tables
  • 1.1.5 (Jan 31, 2023): Fixed bug with large disks (>2TB) introduced with 1.1.4
  • 1.1.6 (Feb 14, 2023): Fixed ReFS support, install from Windows Service, updated cygwin binaries
  • 1.1.7 (Jun 27, 2023): Fixed BSOD on low memory, fixed performance bug, poll_hup support for utils