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Jorgen Lundman edited this page Oct 12, 2025 · 2 revisions

Windows Crash Dumps

Crashdumps can be enabled in Settings > System > Info under "extended system settings" If you do managed to get a Blue Screen Of Death (BSOD), Windows should in theory write a crash dump file to:

 C:\Windows\MEMORY.DMP

The dump file can be analyzed with [http://windbg.org WinDbg.exe]

Debug builds of OpenZFS include debugging symbols to assist in dump analysis which are located at:

 C:\Program Files\OpenZFS On Windows\symbols\

WinDbg.exe at the Command Line

Once installed, WinDbg.exe can be run from a CMD.com or PowerShell terminal with Administrative privileges:

 WinDbgX.exe -y ‘C:\Program Files\OpenZFS On Windows\symbols\’ -z C:\Windows\MEMORY.DMP

This will launch the application and you can perform dump analysis with:

 kd> !analyze -v

To run the analysis in a single command:

 WinDbgX.exe -y ‘C:\Program Files\OpenZFS On Windows\symbols\’ -z C:\Windows\MEMORY.DMP -c !analyze -v

WinDbg.exe in the GUI

Launch WinDbg.exe and set the symbol path:

 kd> .symfix c:\cache
 kd> .sympath+ C:\Program Files\OpenZFS On Windows\symbols
 kd> .reload

So that it can load both the symbols from Microsoft, and from the installed Open ZFS directory.

Open the crash dump file with:

 File: Open crash dump
 C:\Windows\MEMORY.DMP

Perform the analysis:

 kd> !analyze -v

Should at least show the stack.

Minidump walkthrough

  • Set symbol path
    Set symbol path

  • Add path
    Add path

  • Load crash dump
    Load crash dump

  • Locate minidump
    Locate minidump

  • Minidump loading
    Minidump loading

  • Analyze with stack
    Analyze with stack

Example Crash report

A successful crash dump would look something like:

  	OpenZFS!zfs_range_lock_reader+0x290 [c:\src\openzfs\zfs\module\zfs\zfs_rlock.c @ 417]	C/C++/ASM
 	OpenZFS!zfs_range_lock+0x16d [c:\src\openzfs\zfs\module\zfs\zfs_rlock.c @ 453]	C/C++/ASM
 	OpenZFS!zil_lwb_commit+0x99f [c:\src\openzfs\zfs\module\zfs\zil.c @ 1570]	C/C++/ASM
 	OpenZFS!zil_process_commit_list+0x30e [c:\src\openzfs\zfs\module\zfs\zil.c @ 2182]	C/C++/ASM
 	OpenZFS!zil_commit_writer+0x111 [c:\src\openzfs\zfs\module\zfs\zil.c @ 2318]	C/C++/ASM

If you get only OpenZFS+0x"hex-number" it means it is not reading the debug symbols correctly, to be able to convert the hex-number into a function name.

Debug Print Buffer

Windows features a circular debug print buffer which can also be written to disk:

 kd> .writemem C:\Users\<your Windows username>\Desktop\cbuf.txt poi(OpenZFS!cbuf) L100000

Do not worry if you get a message about short write, it just means you have not yet filled the buffer.

This will include -EB- at the end of the buffer. Do not worry if the rest of the buffer has "@" (nul) symbols, it just means the buffer was not yet full.

Please provide the contents of the dump analysis and cbuf.txt in your crash-related tickets.

Other useful debugger commands:

 # Write out OpenZVOL's cbuf instead.
 kd> .writemem zvol_cbuf.txt poi(OpenZVOL!cbuf) L100000

 # Dump all OpenZFS stacks (somewhat slow)
 .logopen c:\src\stacks.txt ; !stacks 2 OpenZFS; .logclose

 # Dump all stacks (definitely slow)
 .logopen c:\src\stacks.txt ; !stacks 2; .logclose

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