Notice

This document is for a development version of Ceph.

OSD Service

List Devices

ceph-volume scans each cluster in the host from time to time in order to determine which devices are present and whether they are eligible to be used as OSDs.

To print a list of devices discovered by cephadm, run this command:

ceph orch device ls [--hostname=...] [--wide] [--refresh]

Example

Hostname  Path      Type  Serial              Size   Health   Ident  Fault  Available
srv-01    /dev/sdb  hdd   15P0A0YFFRD6         300G  Unknown  N/A    N/A    No
srv-01    /dev/sdc  hdd   15R0A08WFRD6         300G  Unknown  N/A    N/A    No
srv-01    /dev/sdd  hdd   15R0A07DFRD6         300G  Unknown  N/A    N/A    No
srv-01    /dev/sde  hdd   15P0A0QDFRD6         300G  Unknown  N/A    N/A    No
srv-02    /dev/sdb  hdd   15R0A033FRD6         300G  Unknown  N/A    N/A    No
srv-02    /dev/sdc  hdd   15R0A05XFRD6         300G  Unknown  N/A    N/A    No
srv-02    /dev/sde  hdd   15R0A0ANFRD6         300G  Unknown  N/A    N/A    No
srv-02    /dev/sdf  hdd   15R0A06EFRD6         300G  Unknown  N/A    N/A    No
srv-03    /dev/sdb  hdd   15R0A0OGFRD6         300G  Unknown  N/A    N/A    No
srv-03    /dev/sdc  hdd   15R0A0P7FRD6         300G  Unknown  N/A    N/A    No
srv-03    /dev/sdd  hdd   15R0A0O7FRD6         300G  Unknown  N/A    N/A    No

Using the --wide option provides all details relating to the device, including any reasons that the device might not be eligible for use as an OSD.

In the above example you can see fields named “Health”, “Ident”, and “Fault”. This information is provided by integration with libstoragemgmt. By default, this integration is disabled (because libstoragemgmt may not be 100% compatible with your hardware). To make cephadm include these fields, enable cephadm’s “enhanced device scan” option as follows;

ceph config set mgr mgr/cephadm/device_enhanced_scan true

Warning

Although the libstoragemgmt library performs standard SCSI inquiry calls, there is no guarantee that your firmware fully implements these standards. This can lead to erratic behaviour and even bus resets on some older hardware. It is therefore recommended that, before enabling this feature, you test your hardware’s compatibility with libstoragemgmt first to avoid unplanned interruptions to services.

There are a number of ways to test compatibility, but the simplest may be to use the cephadm shell to call libstoragemgmt directly - cephadm shell lsmcli ldl. If your hardware is supported you should see something like this:

Path     | SCSI VPD 0x83    | Link Type | Serial Number      | Health Status
----------------------------------------------------------------------------
/dev/sda | 50000396082ba631 | SAS       | 15P0A0R0FRD6       | Good
/dev/sdb | 50000396082bbbf9 | SAS       | 15P0A0YFFRD6       | Good

After you have enabled libstoragemgmt support, the output will look something like this:

# ceph orch device ls
Hostname   Path      Type  Serial              Size   Health   Ident  Fault  Available
srv-01     /dev/sdb  hdd   15P0A0YFFRD6         300G  Good     Off    Off    No
srv-01     /dev/sdc  hdd   15R0A08WFRD6         300G  Good     Off    Off    No
:

In this example, libstoragemgmt has confirmed the health of the drives and the ability to interact with the Identification and Fault LEDs on the drive enclosures. For further information about interacting with these LEDs, refer to device management.

Note

The current release of libstoragemgmt (1.8.8) supports SCSI, SAS, and SATA based local disks only. There is no official support for NVMe devices (PCIe)

Deploy OSDs

Listing Storage Devices

In order to deploy an OSD, there must be a storage device that is available on which the OSD will be deployed.

Run this command to display an inventory of storage devices on all cluster hosts:

ceph orch device ls

A storage device is considered available if all of the following conditions are met:

  • The device must have no partitions.

  • The device must not have any LVM state.

  • The device must not be mounted.

  • The device must not contain a file system.

  • The device must not contain a Ceph BlueStore OSD.

  • The device must be larger than 5 GB.

Ceph will not provision an OSD on a device that is not available.

Creating New OSDs

There are a few ways to create new OSDs:

  • Tell Ceph to consume any available and unused storage device:

    ceph orch apply osd --all-available-devices
    
  • Create an OSD from a specific device on a specific host:

    ceph orch daemon add osd *<host>*:*<device-path>*
    

    For example:

    ceph orch daemon add osd host1:/dev/sdb
    
  • You can use Advanced OSD Service Specifications to categorize device(s) based on their properties. This might be useful in forming a clearer picture of which devices are available to consume. Properties include device type (SSD or HDD), device model names, size, and the hosts on which the devices exist:

    ceph orch apply -i spec.yml
    

Dry Run

The --dry-run flag causes the orchestrator to present a preview of what will happen without actually creating the OSDs.

For example:

ceph orch apply osd --all-available-devices --dry-run
NAME                  HOST  DATA      DB  WAL
all-available-devices node1 /dev/vdb  -   -
all-available-devices node2 /dev/vdc  -   -
all-available-devices node3 /dev/vdd  -   -

Declarative State

Note that the effect of ceph orch apply is persistent; that is, drives which are added to the system or become available (say, by zapping) after the command is complete will be automatically found and added to the cluster.

That is, after using:

ceph orch apply osd --all-available-devices
  • If you add new disks to the cluster they will automatically be used to create new OSDs.

  • A new OSD will be created automatically if you remove an OSD and clean the LVM physical volume.

If you want to avoid this behavior (disable automatic creation of OSD on available devices), use the unmanaged parameter:

ceph orch apply osd --all-available-devices --unmanaged=true

Remove an OSD

Removing an OSD from a cluster involves two steps:

  1. evacuating all placement groups (PGs) from the cluster

  2. removing the PG-free OSD from the cluster

The following command performs these two steps:

ceph orch osd rm <osd_id(s)> [--replace] [--force]

Example:

ceph orch osd rm 0

Expected output:

Scheduled OSD(s) for removal

OSDs that are not safe to destroy will be rejected.

Monitoring OSD State

You can query the state of OSD operation with the following command:

ceph orch osd rm status

Expected output:

OSD_ID  HOST         STATE                    PG_COUNT  REPLACE  FORCE  STARTED_AT
2       cephadm-dev  done, waiting for purge  0         True     False  2020-07-17 13:01:43.147684
3       cephadm-dev  draining                 17        False    True   2020-07-17 13:01:45.162158
4       cephadm-dev  started                  42        False    True   2020-07-17 13:01:45.162158

When no PGs are left on the OSD, it will be decommissioned and removed from the cluster.

Note

After removing an OSD, if you wipe the LVM physical volume in the device used by the removed OSD, a new OSD will be created. For more information on this, read about the unmanaged parameter in Declarative State.

Stopping OSD Removal

It is possible to stop queued OSD removals by using the following command:

ceph orch osd rm stop <svc_id(s)>

Example:

ceph orch osd rm stop 4

Expected output:

Stopped OSD(s) removal

This resets the initial state of the OSD and takes it off the removal queue.

Replacing an OSD

orch osd rm <svc_id(s)> --replace [--force]

Example:

ceph orch osd rm 4 --replace

Expected output:

Scheduled OSD(s) for replacement

This follows the same procedure as the procedure in the “Remove OSD” section, with one exception: the OSD is not permanently removed from the CRUSH hierarchy, but is instead assigned a ‘destroyed’ flag.

Preserving the OSD ID

The ‘destroyed’ flag is used to determine which OSD ids will be reused in the next OSD deployment.

If you use OSDSpecs for OSD deployment, your newly added disks will be assigned the OSD ids of their replaced counterparts. This assumes that the new disks still match the OSDSpecs.

Use the --dry-run flag to make certain that the ceph orch apply osd command does what you want it to. The --dry-run flag shows you what the outcome of the command will be without making the changes you specify. When you are satisfied that the command will do what you want, run the command without the --dry-run flag.

Tip

The name of your OSDSpec can be retrieved with the command ceph orch ls

Alternatively, you can use your OSDSpec file:

ceph orch apply osd -i <osd_spec_file> --dry-run

Expected output:

NAME                  HOST  DATA     DB WAL
<name_of_osd_spec>    node1 /dev/vdb -  -

When this output reflects your intention, omit the --dry-run flag to execute the deployment.

Erasing Devices (Zapping Devices)

Erase (zap) a device so that it can be reused. zap calls ceph-volume zap on the remote host.

orch device zap <hostname> <path>

Example command:

ceph orch device zap my_hostname /dev/sdx

Note

If the unmanaged flag is unset, cephadm automatically deploys drives that match the DriveGroup in your OSDSpec. For example, if you use the all-available-devices option when creating OSDs, when you zap a device the cephadm orchestrator automatically creates a new OSD in the device. To disable this behavior, see Declarative State.

Advanced OSD Service Specifications

Service Specification of type osd are a way to describe a cluster layout using the properties of disks. It gives the user an abstract way tell ceph which disks should turn into an OSD with which configuration without knowing the specifics of device names and paths.

Instead of doing this

ceph orch daemon add osd *<host>*:*<path-to-device>*

for each device and each host, we can define a yaml|json file that allows us to describe the layout. Here’s the most basic example.

Create a file called i.e. osd_spec.yml

service_type: osd
service_id: default_drive_group  <- name of the drive_group (name can be custom)
placement:
  host_pattern: '*'              <- which hosts to target, currently only supports globs
data_devices:                    <- the type of devices you are applying specs to
  all: true                      <- a filter, check below for a full list

This would translate to:

Turn any available(ceph-volume decides what ‘available’ is) into an OSD on all hosts that match the glob pattern ‘*’. (The glob pattern matches against the registered hosts from host ls) There will be a more detailed section on host_pattern down below.

and pass it to osd create like so

ceph orch apply osd -i /path/to/osd_spec.yml

This will go out on all the matching hosts and deploy these OSDs.

Since we want to have more complex setups, there are more filters than just the ‘all’ filter.

Also, there is a –dry-run flag that can be passed to the apply osd command, which gives you a synopsis of the proposed layout.

Example

[monitor.1]# ceph orch apply osd -i /path/to/osd_spec.yml --dry-run

Filters

Note

Filters are applied using a AND gate by default. This essentially means that a drive needs to fulfill all filter criteria in order to get selected. If you wish to change this behavior you can adjust this behavior by setting

filter_logic: OR # valid arguments are AND, OR

in the OSD Specification.

You can assign disks to certain groups by their attributes using filters.

The attributes are based off of ceph-volume’s disk query. You can retrieve the information with

ceph-volume inventory </path/to/disk>

Vendor or Model:

You can target specific disks by their Vendor or by their Model

model: disk_model_name

or

vendor: disk_vendor_name

Size:

You can also match by disk Size.

size: size_spec
Size specs:

Size specification of format can be of form:

  • LOW:HIGH

  • :HIGH

  • LOW:

  • EXACT

Concrete examples:

Includes disks of an exact size

size: '10G'

Includes disks which size is within the range

size: '10G:40G'

Includes disks less than or equal to 10G in size

size: ':10G'

Includes disks equal to or greater than 40G in size

size: '40G:'

Sizes don’t have to be exclusively in Gigabyte(G).

Supported units are Megabyte(M), Gigabyte(G) and Terrabyte(T). Also appending the (B) for byte is supported. MB, GB, TB

Rotational:

This operates on the ‘rotational’ attribute of the disk.

rotational: 0 | 1

1 to match all disks that are rotational

0 to match all disks that are non-rotational (SSD, NVME etc)

All:

This will take all disks that are ‘available’

Note: This is exclusive for the data_devices section.

all: true

Limiter:

When you specified valid filters but want to limit the amount of matching disks you can use the ‘limit’ directive.

limit: 2

For example, if you used vendor to match all disks that are from VendorA but only want to use the first two you could use limit.

data_devices:
  vendor: VendorA
  limit: 2

Note: Be aware that limit is really just a last resort and shouldn’t be used if it can be avoided.

Additional Options

There are multiple optional settings you can use to change the way OSDs are deployed. You can add these options to the base level of a DriveGroup for it to take effect.

This example would deploy all OSDs with encryption enabled.

service_type: osd
service_id: example_osd_spec
placement:
  host_pattern: '*'
data_devices:
  all: true
encrypted: true

See a full list in the DriveGroupSpecs

class ceph.deployment.drive_group.DriveGroupSpec(*args: Any, **kwargs: Any)

Describe a drive group in the same form that ceph-volume understands.

block_db_size: Optional[Union[int, str]]

Set (or override) the “bluestore_block_db_size” value, in bytes

block_wal_size: Optional[Union[int, str]]

Set (or override) the “bluestore_block_wal_size” value, in bytes

data_devices

A ceph.deployment.drive_group.DeviceSelection

data_directories

A list of strings, containing paths which should back OSDs

db_devices

A ceph.deployment.drive_group.DeviceSelection

db_slots

How many OSDs per DB device

encrypted

true or false

filter_logic

The logic gate we use to match disks with filters. defaults to ‘AND’

journal_devices

A ceph.deployment.drive_group.DeviceSelection

journal_size: Optional[Union[int, str]]

set journal_size in bytes

objectstore

filestore or bluestore

osd_id_claims

Optional: mapping of host -> List of osd_ids that should be replaced See OSD Replacement

osds_per_device

Number of osd daemons per “DATA” device. To fully utilize nvme devices multiple osds are required.

preview_only

If this should be treated as a ‘preview’ spec

wal_devices

A ceph.deployment.drive_group.DeviceSelection

wal_slots

How many OSDs per WAL device

Examples

The simple case

All nodes with the same setup

20 HDDs
Vendor: VendorA
Model: HDD-123-foo
Size: 4TB

2 SSDs
Vendor: VendorB
Model: MC-55-44-ZX
Size: 512GB

This is a common setup and can be described quite easily:

service_type: osd
service_id: osd_spec_default
placement:
  host_pattern: '*'
data_devices:
  model: HDD-123-foo <- note that HDD-123 would also be valid
db_devices:
  model: MC-55-44-XZ <- same here, MC-55-44 is valid

However, we can improve it by reducing the filters on core properties of the drives:

service_type: osd
service_id: osd_spec_default
placement:
  host_pattern: '*'
data_devices:
  rotational: 1
db_devices:
  rotational: 0

Now, we enforce all rotating devices to be declared as ‘data devices’ and all non-rotating devices will be used as shared_devices (wal, db)

If you know that drives with more than 2TB will always be the slower data devices, you can also filter by size:

service_type: osd
service_id: osd_spec_default
placement:
  host_pattern: '*'
data_devices:
  size: '2TB:'
db_devices:
  size: ':2TB'

Note: All of the above DriveGroups are equally valid. Which of those you want to use depends on taste and on how much you expect your node layout to change.

The advanced case

Here we have two distinct setups

20 HDDs
Vendor: VendorA
Model: HDD-123-foo
Size: 4TB

12 SSDs
Vendor: VendorB
Model: MC-55-44-ZX
Size: 512GB

2 NVMEs
Vendor: VendorC
Model: NVME-QQQQ-987
Size: 256GB
  • 20 HDDs should share 2 SSDs

  • 10 SSDs should share 2 NVMes

This can be described with two layouts.

service_type: osd
service_id: osd_spec_hdd
placement:
  host_pattern: '*'
data_devices:
  rotational: 0
db_devices:
  model: MC-55-44-XZ
  limit: 2 (db_slots is actually to be favoured here, but it's not implemented yet)
---
service_type: osd
service_id: osd_spec_ssd
placement:
  host_pattern: '*'
data_devices:
  model: MC-55-44-XZ
db_devices:
  vendor: VendorC

This would create the desired layout by using all HDDs as data_devices with two SSD assigned as dedicated db/wal devices. The remaining SSDs(8) will be data_devices that have the ‘VendorC’ NVMEs assigned as dedicated db/wal devices.

The advanced case (with non-uniform nodes)

The examples above assumed that all nodes have the same drives. That’s however not always the case.

Node1-5

20 HDDs
Vendor: Intel
Model: SSD-123-foo
Size: 4TB
2 SSDs
Vendor: VendorA
Model: MC-55-44-ZX
Size: 512GB

Node6-10

5 NVMEs
Vendor: Intel
Model: SSD-123-foo
Size: 4TB
20 SSDs
Vendor: VendorA
Model: MC-55-44-ZX
Size: 512GB

You can use the ‘host_pattern’ key in the layout to target certain nodes. Salt target notation helps to keep things easy.

service_type: osd
service_id: osd_spec_node_one_to_five
placement:
  host_pattern: 'node[1-5]'
data_devices:
  rotational: 1
db_devices:
  rotational: 0
---
service_type: osd
service_id: osd_spec_six_to_ten
placement:
  host_pattern: 'node[6-10]'
data_devices:
  model: MC-55-44-XZ
db_devices:
  model: SSD-123-foo

This applies different OSD specs to different hosts depending on the host_pattern key.

Dedicated wal + db

All previous cases co-located the WALs with the DBs. It’s however possible to deploy the WAL on a dedicated device as well, if it makes sense.

20 HDDs
Vendor: VendorA
Model: SSD-123-foo
Size: 4TB

2 SSDs
Vendor: VendorB
Model: MC-55-44-ZX
Size: 512GB

2 NVMEs
Vendor: VendorC
Model: NVME-QQQQ-987
Size: 256GB

The OSD spec for this case would look like the following (using the model filter):

service_type: osd
service_id: osd_spec_default
placement:
  host_pattern: '*'
data_devices:
  model: MC-55-44-XZ
db_devices:
  model: SSD-123-foo
wal_devices:
  model: NVME-QQQQ-987

It is also possible to specify directly device paths in specific hosts like the following:

service_type: osd
service_id: osd_using_paths
placement:
  hosts:
    - Node01
    - Node02
data_devices:
  paths:
    - /dev/sdb
db_devices:
  paths:
    - /dev/sdc
wal_devices:
  paths:
    - /dev/sdd

This can easily be done with other filters, like size or vendor as well.

Activate existing OSDs

In case the OS of a host was reinstalled, existing OSDs need to be activated again. For this use case, cephadm provides a wrapper for activate that activates all existing OSDs on a host.

ceph cephadm osd activate <host>...

This will scan all existing disks for OSDs and deploy corresponding daemons.