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About

Ceph Windows support is currently a work in progress. For now, the main focus is the client side, allowing Windows hosts to consume rados, rbd and cephfs resources.

Building

At the moment, mingw gcc >= 8 is the only supported compiler for building ceph components for Windows. Support for msvc and clang will be added soon.

win32_build.sh can be used for cross compiling Ceph and its dependencies. It may be called from a Linux environment, including Windows Subsystem for Linux. MSYS2 and CygWin may also work but those weren't tested.

This script currently supports Ubuntu 18.04 and openSUSE Tumbleweed, but it may be easily adapted to run on other Linux distributions, taking into account different package managers, package names or paths (e.g. mingw paths).

The script accepts the following flags:

Flag Description Default value
OS Host OS distribution, for mingw and other OS specific settings. ubuntu (also valid: suse)
CEPH_DIR The Ceph source code directory. The same as the script.
BUILD_DIR The directory where the generated artifacts will be placed. $CEPH_DIR/build
DEPS_DIR The directory where the Ceph dependencies will be built. $CEPH_DIR/build.deps
NUM_WORKERS The number of workers to use when building Ceph. The number of vcpus available
CLEAN_BUILD Clean the build directory.  
SKIP_BUILD Run cmake without actually performing the build.  
SKIP_TESTS Skip building Ceph tests.  
SKIP_ZIP If unset, we'll build a zip archive containing the generated binaries.  
ZIP_DEST Where to put a zip containing the generated binaries. $BUILD_DIR/ceph.zip
EMBEDDED_DBG_SYM By default, the generated archive will contain a .debug subfolder, having the debug symbols. If this flag is set, the debug symbols will remain embedded in the executables.  
ENABLE_SHARED Dynamically link Ceph libs. False

The following command will build the binaries and add them to a zip archive along with all the required DLLs. By default, the debug symbols are extracted from the binaries and placed in the ".debug" folder of the archive.

SKIP_TESTS=1 ./win32_build.sh

In order to disable a flag, such as CLEAN_BUILD, leave it undefined.

win32_build.sh will fetch dependencies using win32_deps_build.sh. If all dependencies are successfully prepared, this potentially time consuming step will be skipped by subsequent builds. Be aware that you may have to do a clean build (using the CLEAN_BUILD flag) when the dependencies change (e.g. after switching to a more recent Ceph version by doing a git pull).

Make sure to explicitly pass the "OS" parameter when directly calling win32_deps_build.sh. Also, be aware of the fact that it will use the distro specific package manager, which will require privileged rights.

Current status

Ceph filesystems can be mounted using the ceph-dokan command, which requires the Dokany package to be installed. Note that dokany is a well maintained fork of the Dokan project, allowing filesystems to be implemented in userspace, pretty much like Fuse.

RBD images can be mounted using the rbd or rbd-wnbd commands. The WNBD driver is required for mapping RBD images on Windows.

A significant number of tests from the tests directory have been ported, providing adequate coverage.

Supported platforms

Windows Server 2019 and Windows Server 2016 are supported. Previous Windows Server versions, including Windows client versions such as Windows 10, might work but haven't been tested.

Windows Server 2016 does not provide unix sockets, in which case the Ceph admin socket feature will be unavailable.

Compatibility

RBD images can be exposed to the OS and host Windows partitions or they can be attached to Hyper-V VMs in the same way as iSCSI disks.

At the moment, the Microsoft Failover Cluster can't use WNBD disks as Cluster Shared Volumes (CSVs) underlying storage. The main reason is that WNBD and rbd-wnbd don't support the SCSI Persistent Reservations feature yet.

OpenStack integration has been proposed as well and will most probably be included in the next OpenStack release, allowing RBD images managed by OpenStack Cinder to be attached to Hyper-V VMs managed by OpenStack Nova.

Installing

The following project allows building an MSI installer that bundles ceph and the WNBD driver: https://github.com/cloudbase/ceph-windows-installer

In order to manually install ceph, start by unzipping the binaries that you may have obtained by following the building step.

You may want to update the environment PATH variable, including the Ceph path. Assuming that you've copied the Ceph binaries to C:\Ceph, you may use the following Powershell command:

[Environment]::SetEnvironmentVariable("Path", "$env:PATH;C:\ceph", "Machine")

In order to mount Ceph filesystems, you will have to install Dokany. You may fetch the installer as well as the source code from the Dokany Github repository: https://github.com/dokan-dev/dokany/releases

Make sure to use 1.3.1, which at time of the writing is the latest stable release.

In order to map RBD images, the WNBD driver must be installed. Please check out this page for more details about WNBD and the install process: https://github.com/cloudbase/wnbd

Configuring

ceph.conf

The default location for the ceph.conf file on Windows is %ProgramData%\ceph\ceph.conf, which usually expands to C:\ProgramData\ceph\ceph.conf.

Below you may find a sample. Please fill in the monitor addresses accordingly.

[global]
    log to stderr = true

    run dir = C:/ProgramData/ceph/out
    crash dir = C:/ProgramData/ceph/out
[client]
    keyring = C:/ProgramData/ceph/keyring
    ; log file = C:/ProgramData/ceph/out/$name.$pid.log
    admin socket = C:/ProgramData/ceph/out/$name.$pid.asok
[global]
    mon host =  [v2:xx.xx.xx.xx:40623,v1:xx.xx.xx.xx:40624] [v2:xx.xx.xx.xx:40625,v1:xx.xx.xx.xx:40626] [v2:xx.xx.xx.xx:40627,v1:xx.xx.xx.xx:40628]

Assuming that you're going to use this config sample, don't forget to also copy your keyring file to the specified location and make sure that the configured directories exist (e.g. C:\ProgramData\ceph\out).

Please use slashes / instead of backslashes \ as path separators within ceph.conf for the time being.

Windows service

On Windows, rbd-wnbd daemons are managed by a centralized service. This allows decoupling the daemons from the Windows session from which they originate. At the same time, the service is responsible of recreating persistent mappings, usually when the host boots.

Note that only one such service may run per host.

By default, all image mappings are persistent. Non-persistent mappings can be requested using the -onon-persistent rbd flag.

Persistent mappings are recreated when the service starts, unless explicitly unmapped. The service disconnects the mappings when being stopped. This also allows adjusting the Windows service start order so that rbd images can be mapped before starting services that may depend on it, such as VMMS.

In order to be able to reconnect the images, rbd-wnbd stores mapping information in the Windows registry at the following location: SYSTEM\CurrentControlSet\Services\rbd-wnbd.

The following command can be used to configure the service. Please update the rbd-wnbd.exe path accordingly.

New-Service -Name "ceph-rbd" `
            -Description "Ceph RBD Mapping Service" `
            -BinaryPathName "c:\ceph\rbd-wnbd.exe service" `
            -StartupType Automatic

Usage

Cephfs

In order to mount a ceph filesystem, the following command can be used:

ceph-dokan.exe -c c:\ceph.conf -l x

The above command will mount the default ceph filesystem using the drive letter x. If ceph.conf is placed at the default location, which is %ProgramData%\ceph\ceph.conf, then this argument becomes optional.

The -l argument also allows using an empty folder as a mountpoint instead of a drive letter.

The uid and gid used for mounting the filesystem defaults to 0 and may be changed using the -u and -g arguments. -n can be used in order to skip enforcing permissions on client side. Be aware that Windows ACLs are ignored. Posix ACLs are supported but cannot be modified using the current CLI. In the future, we may add some command actions to change file ownership or permissions.

For debugging purposes, -d and s might be used. The first one will enable debug output and the latter will enable stderr logging. By default, debug messages are sent to a connected debugger.

You may use --help to get the full list of available options. The current syntax is up for discussion and might change.

RBD

The rbd command can be used to create, remove, import, export, map or unmap images exactly like it would on Linux.

Mapping images

In order to map RBD images, please install WNBD, as mentioned by the installing guide.

The behavior and CLI is similar to the Linux counterpart, with a few notable differences:

  • device paths cannot be requested. The disk number and path will be picked by Windows. If a device path is provided by the used when mapping an image, it will be used as an identifier, which can also be used when unmapping the image.
  • the show command was added, which describes a specific mapping. This can be used for retrieving the disk path.
  • the service command was added, allowing rbd-wnbd to run as a Windows service. All mappings are currently perisistent, being recreated when the service stops, unless explicitly unmapped. The service disconnects the mappings when being stopped.
  • the list command also includes a status column.

The purpose of the service mode is to ensure that mappings survive reboots and that the Windows service start order can be adjusted so that rbd images can be mapped before starting services that may depend on it, such as VMMS.

Please follow the windows_service guide in order to configure the service.

The mapped images can either be consumed by the host directly or exposed to Hyper-V VMs.

Hyper-V VM disks

The following sample imports an RBD image and boots a Hyper-V VM using it.

# Feel free to use any other image. This one is convenient to use for
# testing purposes because it's very small (~15MB) and the login prompt
# prints the pre-configured password.
wget http://download.cirros-cloud.net/0.5.1/cirros-0.5.1-x86_64-disk.img `
     -OutFile cirros-0.5.1-x86_64-disk.img

# We'll need to make sure that the imported images are raw (so no qcow2 or vhdx).
# You may get qemu-img from https://cloudbase.it/qemu-img-windows/
# You can add the extracted location to $env:Path or update the path accordingly.
qemu-img convert -O raw cirros-0.5.1-x86_64-disk.img cirros-0.5.1-x86_64-disk.raw

rbd import cirros-0.5.1-x86_64-disk.raw
# Let's give it a hefty 100MB size.
rbd resize cirros-0.5.1-x86_64-disk.raw --size=100MB

rbd device map cirros-0.5.1-x86_64-disk.raw

# Let's have a look at the mappings.
rbd device list
Get-Disk

$mappingJson = rbd-wnbd show cirros-0.5.1-x86_64-disk.raw --format=json
$mappingJson = $mappingJson | ConvertFrom-Json

$diskNumber = $mappingJson.disk_number

New-VM -VMName BootFromRBD -MemoryStartupBytes 512MB
# The disk must be turned offline before it can be passed to Hyper-V VMs
Set-Disk -Number $diskNumber -IsOffline $true
Add-VMHardDiskDrive -VMName BootFromRBD -DiskNumber $diskNumber
Start-VM -VMName BootFromRBD
Windows partitions

The following sample creates an empty RBD image, attaches it to the host and initializes a partition.

rbd create blank_image --size=1G
rbd device map blank_image -onon-persistent

$mappingJson = rbd-wnbd show blank_image --format=json
$mappingJson = $mappingJson | ConvertFrom-Json

$diskNumber = $mappingJson.disk_number

# The disk must be online before creating or accessing partitions.
Set-Disk -Number $diskNumber -IsOffline $false

# Initialize the disk, partition it and create a fileystem.
Get-Disk -Number $diskNumber | `
    Initialize-Disk -PassThru | `
    New-Partition -AssignDriveLetter -UseMaximumSize | `
    Format-Volume -Force -Confirm:$false

Troubleshooting

Wnbd

For WNBD troubleshooting, please check this page: https://github.com/cloudbase/wnbd#troubleshooting

Privileges

Most rbd-wnbd and rbd device commands require privileged rights. Make sure to use an elevated PowerShell or CMD command prompt.

Crash dumps

Userspace crash dumps can be placed at a configurable location and enabled for all applications or just predefined ones, as outlined here: https://docs.microsoft.com/en-us/windows/win32/wer/collecting-user-mode-dumps.

Whenever a Windows application crashes, an event will be submitted to the Application Windows Event Log, having Event ID 1000. The entry will also include the process id, the faulting module name and path as well as the exception code.

Please note that in order to analyze crash dumps, the debug symbols are required. We're currently buidling Ceph using MinGW, so by default DWARF symbols will be embedded in the binaries. windbg does not support such symbols but gdb can be used.

gdb can debug running Windows processes but it cannot open Windows minidumps. The following gdb fork may be used until this functionality is merged upstream: https://github.com/ssbssa/gdb/releases. As an alternative, DWARF symbols can be converted using cv2pdb but be aware that this tool has limitted C++ support.

ceph tool

The ceph Python tool can't be used on Windows natively yet. With minor changes it may run, but the main issue is that Python doesn't currently allow using AF_UNIX on Windows: https://bugs.python.org/issue33408

As an alternative, the ceph tool can be used through Windows Subsystem for Linux (WSL). For example, running Windows RBD daemons may be contacted by using:

ceph daemon /mnt/c/ProgramData/ceph/out/ceph-client.admin.61436.1209215304.asok help
IO counters

Along with the standard RBD perf counters, the libwnbd IO counters may be retrieved using:

rbd-wnbd stats $imageName

At the same time, WNBD driver counters can be fetched using:

wnbd-client stats $mappingId

Note that the wnbd-client mapping identifier will be the full RBD image spec (the device column of the rbd device list output).