ceph-volume
ceph-volume is a Ceph tool used to manage and provision OSDs (Object Storage Daemons) on a Ceph cluster. It supports various types of storage backends (e.g., lvm, raw, bluestore, filestore) and provides functionality for creating, listing, and destroying OSDs.
Here are the relevant subcommands and their common usage:
Common ceph-volume Subcommands
ceph-volume Subcommands1. ceph-volume lvm
The ceph-volume lvm subcommand is used to manage OSDs backed by LVM (Logical Volume Manager). Ceph OSDs are often deployed using bluestore or filestore on LVM partitions.
ceph-volume lvm create
ceph-volume lvm createCreates a new OSD backed by LVM.
Example:
This command creates a new OSD on the device /dev/sdb. By default, it creates a bluestore OSD, but you can specify filestore if needed:
Example for
filestore:
ceph-volume lvm list
ceph-volume lvm listLists all OSDs that are backed by LVM.
Example:
This displays detailed information about all LVM-backed OSDs in the system.
ceph-volume lvm zap
ceph-volume lvm zapDestroys the contents of a device (zaps) to prepare it for reuse.
Example:
This wipes all data and partitioning information from the device /dev/sdb, making it ready for new OSD creation.
ceph-volume lvm activate
ceph-volume lvm activateActivates an existing OSD by associating it with the Ceph cluster.
Example:
This activates all LVM-backed OSDs in the system, making them part of the running Ceph cluster.
2. ceph-volume raw
The ceph-volume raw subcommand is used to manage OSDs without LVM, particularly for bluestore OSDs that don't require LVM as a backend.
ceph-volume raw create
ceph-volume raw createCreates a new OSD without LVM.
Example:
This creates a bluestore OSD on the raw device /dev/sdc without using LVM.
ceph-volume raw list
ceph-volume raw listLists all OSDs that are not backed by LVM (raw OSDs).
Example:
This displays detailed information about all raw OSDs in the system.
ceph-volume raw zap
ceph-volume raw zapZaps (wipes) a raw device to prepare it for reuse.
Example:
This wipes all data and partitioning information from the raw device /dev/sdc, preparing it for reuse.
3. ceph-volume simple
The ceph-volume simple subcommand is a legacy command used to manage OSDs before lvm and raw methods were introduced. It's now deprecated but still supported for backward compatibility.
ceph-volume simple scan
ceph-volume simple scanScans a device to gather information about existing OSDs.
Example:
This scans the device /dev/sdd to check if an OSD is already present or if it can be reused.
ceph-volume simple activate
ceph-volume simple activateActivates an existing OSD using the legacy simple method.
Example:
This activates all OSDs managed by the simple backend.
4. ceph-volume inventory
The ceph-volume inventory subcommand is used to display the inventory of available devices that can be used for OSD creation.
ceph-volume inventory
ceph-volume inventoryLists all available devices on the host that can be used for OSD creation, showing if they are zapped, have partitions, or contain OSDs.
Example:
This command provides detailed information about all devices available for OSD use on the system, indicating their status.
5. ceph-volume trigger
The ceph-volume trigger subcommand allows manual triggering of specific events for OSDs, such as triggering a rescan of LVM devices.
ceph-volume trigger rescan
ceph-volume trigger rescanTriggers a rescan of LVM devices to ensure that all OSDs are properly detected and activated.
Example:
This forces a rescan of LVM devices, ensuring that the cluster has up-to-date information on all OSDs.
6. ceph-volume systemd
The ceph-volume systemd subcommand helps manage the interaction between OSDs and systemd units for service management.
ceph-volume systemd list
ceph-volume systemd listLists all the systemd unit files related to OSDs.
Example:
This command displays all the systemd units managing OSDs, showing their statuses.
ceph-volume systemd activate
ceph-volume systemd activateActivates systemd unit files for OSDs.
Example:
This activates all the systemd unit files responsible for managing the OSDs.
Conclusion
The ceph-volume tool is essential for managing the lifecycle of Ceph OSDs, offering flexibility in choosing between LVM and raw devices. Its subcommands allow you to create, list, activate, and zap OSDs, and manage the inventory of available devices. By providing options for both legacy and modern methods of OSD provisioning, ceph-volume ensures the robust and efficient management of Ceph storage resources.
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