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185 lines
7.0 KiB
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==============
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RBD on Windows
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==============
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The ``rbd`` command can be used to create, remove, import, export, map or
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unmap images exactly like it would on Linux. Make sure to check the
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`RBD basic commands`_ guide.
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``librbd.dll`` is also available for applications that can natively use Ceph.
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Please check the `installation guide`_ to get started.
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Windows service
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===============
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On Windows, ``rbd-wnbd`` daemons are managed by a centralized service. This allows
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decoupling the daemons from the Windows session from which they originate. At
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the same time, the service is responsible of recreating persistent mappings,
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usually when the host boots.
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Note that only one such service may run per host.
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By default, all image mappings are persistent. Non-persistent mappings can be
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requested using the ``-onon-persistent`` ``rbd`` flag.
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Persistent mappings are recreated when the service starts, unless explicitly
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unmapped. The service disconnects the mappings when being stopped. This also
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allows adjusting the Windows service start order so that RBD images can be
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mapped before starting services that may depend on it, such as VMMS.
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In order to be able to reconnect the images, ``rbd-wnbd`` stores mapping
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information in the Windows registry at the following location:
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``SYSTEM\CurrentControlSet\Services\rbd-wnbd``.
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The following command can be used to configure the service. Please update
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the ``rbd-wnbd.exe`` path accordingly::
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New-Service -Name "ceph-rbd" `
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-Description "Ceph RBD Mapping Service" `
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-BinaryPathName "c:\ceph\rbd-wnbd.exe service" `
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-StartupType Automatic
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Note that the Ceph MSI installer takes care of creating the ``ceph-rbd``
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Windows service.
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Usage
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=====
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Integration
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-----------
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RBD images can be exposed to the OS and host Windows partitions or they can be
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attached to Hyper-V VMs in the same way as iSCSI disks.
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Starting with Openstack Wallaby, the Nova Hyper-V driver can attach RBD Cinder
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volumes to Hyper-V VMs.
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Mapping images
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--------------
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The workflow and CLI is similar to the Linux counterpart, with a few
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notable differences:
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* device paths cannot be requested. The disk number and path will be picked by
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Windows. If a device path is provided by the used when mapping an image, it
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will be used as an identifier, which can also be used when unmapping the
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image.
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* the ``show`` command was added, which describes a specific mapping.
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This can be used for retrieving the disk path.
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* the ``service`` command was added, allowing ``rbd-wnbd`` to run as a Windows service.
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All mappings are by default persistent, being recreated when the service
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stops, unless explicitly unmapped. The service disconnects the mappings
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when being stopped.
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* the ``list`` command also includes a ``status`` column.
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The purpose of the ``service`` mode is to ensure that mappings survive reboots
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and that the Windows service start order can be adjusted so that RBD images can
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be mapped before starting services that may depend on it, such as VMMS.
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The mapped images can either be consumed by the host directly or exposed to
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Hyper-V VMs.
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Hyper-V VM disks
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----------------
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The following sample imports an RBD image and boots a Hyper-V VM using it::
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# Feel free to use any other image. This one is convenient to use for
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# testing purposes because it's very small (~15MB) and the login prompt
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# prints the pre-configured password.
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wget http://download.cirros-cloud.net/0.5.1/cirros-0.5.1-x86_64-disk.img `
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-OutFile cirros-0.5.1-x86_64-disk.img
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# We'll need to make sure that the imported images are raw (so no qcow2 or vhdx).
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# You may get qemu-img from https://cloudbase.it/qemu-img-windows/
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# You can add the extracted location to $env:Path or update the path accordingly.
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qemu-img convert -O raw cirros-0.5.1-x86_64-disk.img cirros-0.5.1-x86_64-disk.raw
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rbd import cirros-0.5.1-x86_64-disk.raw
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# Let's give it a hefty 100MB size.
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rbd resize cirros-0.5.1-x86_64-disk.raw --size=100MB
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rbd device map cirros-0.5.1-x86_64-disk.raw
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# Let's have a look at the mappings.
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rbd device list
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Get-Disk
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$mappingJson = rbd-wnbd show cirros-0.5.1-x86_64-disk.raw --format=json
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$mappingJson = $mappingJson | ConvertFrom-Json
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$diskNumber = $mappingJson.disk_number
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New-VM -VMName BootFromRBD -MemoryStartupBytes 512MB
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# The disk must be turned offline before it can be passed to Hyper-V VMs
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Set-Disk -Number $diskNumber -IsOffline $true
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Add-VMHardDiskDrive -VMName BootFromRBD -DiskNumber $diskNumber
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Start-VM -VMName BootFromRBD
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Windows partitions
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------------------
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The following sample creates an empty RBD image, attaches it to the host and
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initializes a partition::
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rbd create blank_image --size=1G
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rbd device map blank_image -onon-persistent
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$mappingJson = rbd-wnbd show blank_image --format=json
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$mappingJson = $mappingJson | ConvertFrom-Json
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$diskNumber = $mappingJson.disk_number
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# The disk must be online before creating or accessing partitions.
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Set-Disk -Number $diskNumber -IsOffline $false
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# Initialize the disk, partition it and create a filesystem.
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Get-Disk -Number $diskNumber | `
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Initialize-Disk -PassThru | `
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New-Partition -AssignDriveLetter -UseMaximumSize | `
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Format-Volume -Force -Confirm:$false
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Limitations
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-----------
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CSV support
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~~~~~~~~~~~
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At the moment, the Microsoft Failover Cluster can't use WNBD disks as
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Cluster Shared Volumes (CSVs) underlying storage. The main reason is that
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``WNBD`` and ``rbd-wnbd`` don't support the *SCSI Persistent Reservations*
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feature yet.
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Hyper-V disk addressing
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~~~~~~~~~~~~~~~~~~~~~~~
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.. warning::
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Hyper-V identifies passthrough VM disks by number instead of SCSI ID, although
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the disk number can change across host reboots. This means that the VMs can end
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up using incorrect disks after rebooting the host, which is an important
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security concern. This issue also affects iSCSI and Fibre Channel disks.
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There are a few possible ways of avoiding this Hyper-V limitation:
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* use an NTFS/ReFS partition to store VHDX image files instead of directly
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attaching the RBD image. This may slightly impact the IO performance.
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* use the Hyper-V ``AutomaticStartAction`` setting to prevent the VMs from
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booting with the incorrect disks and have a script that updates VM disks
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attachments before powering them back on. The ``ElementName`` field of the
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`Msvm_StorageAllocationSettingData`_ `WMI`_ class may be used to label VM
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disk attachments.
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* use the Openstack Hyper-V driver, which automatically refreshes the VM disk
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attachments before powering them back on.
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Troubleshooting
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===============
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Please consult the `Windows troubleshooting`_ page.
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.. _Windows troubleshooting: ../../install/windows-troubleshooting
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.. _installation guide: ../../install/windows-install
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.. _RBD basic commands: ../rados-rbd-cmds
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.. _WNBD driver: https://github.com/cloudbase/wnbd
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.. _Msvm_StorageAllocationSettingData: https://docs.microsoft.com/en-us/windows/win32/hyperv_v2/msvm-storageallocationsettingdata
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.. _WMI: https://docs.microsoft.com/en-us/windows/win32/wmisdk/wmi-start-page
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