doc/cephadm/services/osd.rst
OSD Service
.. _libstoragemgmt: https://github.com/libstorage/libstoragemgmt
ceph-volume scans each host in the cluster periodically in order
to determine the devices that are present and responsive. It is also
determined whether each is eligible to be used for new OSDs in a block,
DB, or WAL role.
To print a list of devices discovered by cephadm, run this command:
.. prompt:: bash #
ceph orch device ls [--hostname=...] [--wide] [--refresh]
Example:
.. code-block:: console
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
In the above examples 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 direct Ceph to include these fields,
enable cephadm's "enhanced device scan" option as follows:
.. prompt:: bash #
ceph config set mgr mgr/cephadm/device_enhanced_scan true
Note that the columns reported by ceph orch device ls may vary from release to
release.
The --wide option shows device details,
including any reasons that the device might not be eligible for use as an OSD.
Example (Reef):
.. code-block:: console
HOST PATH TYPE DEVICE ID SIZE AVAILABLE REFRESHED REJECT REASONS davidsthubbins /dev/sdc hdd SEAGATE_ST20000NM002D_ZVTBJNGC17010W339UW25 18.1T No 22m ago Has a FileSystem, Insufficient space (<10 extents) on vgs, LVM detected nigeltufnel /dev/sdd hdd SEAGATE_ST20000NM002D_ZVTBJNGC17010C3442787 18.1T No 22m ago Has a FileSystem, Insufficient space (<10 extents) on vgs, LVM detected
.. warning::
Although the libstoragemgmt library issues standard SCSI (SES) inquiry calls,
there is no guarantee that your hardware and firmware properly implement these standards.
This can lead to erratic behavior and even bus resets on some older
hardware. It is therefore recommended that, before enabling this feature,
you first test your hardware's compatibility with libstoragemgmt to avoid
unplanned interruptions to services.
There are a number of ways to test compatibility, but the simplest is
to use the cephadm shell to call ``libstoragemgmt`` directly: ``cephadm shell
lsmcli ldl``. If your hardware is supported you should see something like
this:
.. code-block:: console
Path | SCSI VPD 0x83 | Link Type | Serial Number | Health Status
----------------------------------------------------------------------------
/dev/sda | 50000396082ba631 | SAS | 15P0A0R0FRD6 | Good
/dev/sdb | 50000396082bbbf9 | SAS | 15P0A0YFFRD6 | Good
After enabling libstoragemgmt support, the output will look something
like this:
.. prompt:: bash #
ceph orch device ls
.. code-block:: console
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 :ref:devices.
.. note::
The current release of libstoragemgmt (1.8.8) supports SCSI, SAS, and SATA based
local drives only. There is no official support for NVMe devices (PCIe), SAN LUNs,
or exotic/complex metadevices.
Run a command of the following form to discover the exact size of a block device. The value returned here is used by the orchestrator when filtering based on size:
.. prompt:: bash #
cephadm shell ceph-volume inventory </dev/sda> --format json | jq .sys_api.human_readable_size
The exact size in GB is the size reported in TB, multiplied by 1024.
The following provides a specific example of this command based upon the general form of the command above:
.. prompt:: bash #
cephadm shell ceph-volume inventory /dev/sdc --format json | jq .sys_api.human_readable_size
.. code-block:: console
"3.64 TB"
This indicates that the exact device size is 3.64 TB, or 3727.36 GB.
This procedure was developed by Frédéric Nass. See this thread on the [ceph-users] mailing list <https://lists.ceph.io/hyperkitty/list/[email protected]/message/5BAAYFCQAZZDRSNCUPCVBNEPGJDARRZA/>_
for discussion of this matter.
.. _cephadm-deploy-osds:
In order to deploy an OSD, there must be an available storage device or devices on which the OSD will be deployed.
Run this command to display an inventory of storage devices on all cluster hosts:
.. prompt:: bash #
ceph orch device ls
A storage device is considered available if all of the following conditions are met:
Ceph will not provision an OSD on a device that is not available.
There are multiple ways to create new OSDs:
Consume any available and unused storage device:
.. prompt:: bash #
ceph orch apply osd --all-available-devices
Create an OSD from a specific device on a specific host:
.. prompt:: bash #
ceph orch daemon add osd <host>:<device-path>
For example:
.. prompt:: bash #
ceph orch daemon add osd host1:/dev/sdb
Advanced OSD creation from specific devices on a specific host:
.. prompt:: bash #
ceph orch daemon add osd host1:data_devices=/dev/sda,/dev/sdb,db_devices=/dev/sdc,osds_per_device=2
Create an OSD on a specific LVM logical volume on a specific host:
.. prompt:: bash #
ceph orch daemon add osd <host>:<lvm-path>
For example:
.. prompt:: bash #
ceph orch daemon add osd host1:/dev/vg_osd/lvm_osd1701
You can use :ref:drivegroups to categorize devices based on their
properties. This is useful to clarify 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:
.. prompt:: bash #
ceph orch apply -i spec.yml
.. warning:: When deploying new OSDs with cephadm, ensure that the ceph-osd package is not installed on the target host. If it is installed, conflicts may arise in the management and control of the OSD that may lead to errors or unexpected behavior.
New OSDs created using ceph orch daemon add osd are added under osd.default as managed OSDs with a valid spec.
To attach an existing OSD to a different managed service, ceph orch osd set-spec-affinity command can be used:
.. prompt:: bash #
ceph orch osd set-spec-affinity <service_name> <osd_id(s)>
For example:
.. prompt:: bash #
ceph orch osd set-spec-affinity osd.default_drive_group 0 1
The --dry-run flag causes the orchestrator to present a preview of what
will happen without actually creating the OSDs.
For example:
.. prompt:: bash #
ceph orch apply osd --all-available-devices --dry-run
.. code-block:: console
NAME HOST DATA DB WAL all-available-devices node1 /dev/vdb - - all-available-devices node2 /dev/vdc - - all-available-devices node3 /dev/vdd - -
.. _cephadm-osd-declarative:
The effect of ceph orch apply is persistent. This means that drives that
are added to the system after the ceph orch apply command completes will be
automatically detected and added to the cluster as specified. It also means that drives that
become available (e.g. by zapping) after the ceph orch apply
command completes will be automatically found and added to the cluster.
We will examine the effects of the following command:
.. prompt:: bash #
ceph orch apply osd --all-available-devices
After running the above command:
If you want to avoid this behavior (disable automatic creation of OSD on available devices), use the unmanaged parameter:
.. prompt:: bash #
ceph orch apply osd --all-available-devices --unmanaged=true
.. note::
Keep these three facts in mind:
- The default behavior of ``ceph orch apply`` causes ``cephadm`` to constantly reconcile. This means that ``cephadm`` creates OSDs as soon as new drives are detected.
- Setting ``unmanaged: True`` disables the creation of OSDs. If ``unmanaged: True`` is set, nothing will happen even if you apply a new OSD service.
- ``ceph orch daemon add`` creates OSDs, but does not add an OSD service.
For more on cephadm, see also :ref:cephadm-spec-unmanaged.
.. _cephadm-osd-removal:
Removing an OSD from a cluster involves two steps:
#. Evacuating all placement groups (PGs) from the OSD #. Removing the PG-free OSD from the cluster
The following command performs these two steps:
.. prompt:: bash #
ceph orch osd rm <osd_id(s)> [--replace] [--force] [--zap]
Example:
.. prompt:: bash #
ceph orch osd rm 0 ceph orch osd rm 1138 --zap
Expected output:
.. code-block:: console
Scheduled OSD(s) for removal
OSDs that are not safe to destroy will be rejected. Adding the --zap flag
directs the orchestrator to remove all LVM and partition information from the
OSD's drives, leaving it a blank slate for redeployment or other reuse.
.. note::
After removing OSDs, if the OSDs' drives
become available, cephadm may automatically try to deploy more OSDs
on these drives if they match an existing drivegroup spec. If you deployed
the OSDs you are removing with a spec and don't want any new OSDs deployed on
the drives after removal, it's best to modify the drivegroup spec before removal.
Either set unmanaged: true to stop it from picking up new drives,
or modify it in some way that it no longer matches the drives used for the
OSDs you wish to remove. Then re-apply the spec. For more info on drivegroup
specs see :ref:drivegroups. For more info on the declarative nature of
cephadm in reference to deploying OSDs, see :ref:cephadm-osd-declarative.
You can query the state of OSD operations during the process of removing OSDs by running the following command:
.. prompt:: bash #
ceph orch osd rm status
Expected output:
.. code-block:: console
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 :ref:cephadm-osd-declarative.
It is possible to stop queued OSD removals by using the following command:
.. prompt:: bash #
ceph orch osd rm stop <osd_id(s)>
Example:
.. prompt:: bash #
ceph orch osd rm stop 4
Expected output:
.. code-block:: console
Stopped OSD(s) removal
This resets the state of the OSD and takes it off the removal queue.
.. _cephadm-replacing-an-osd:
.. prompt:: bash #
ceph orch osd rm <osd_id(s)> --replace [--force]
Example:
.. prompt:: bash #
ceph orch osd rm 4 --replace
Expected output:
.. code-block:: console
Scheduled OSD(s) for replacement
This follows the same procedure as the procedure in the :ref:cephadm-osd-removal section, with
one exception: the OSD is not permanently removed from the CRUSH hierarchy, but is
instead assigned the destroyed flag.
.. note:: The new OSD that will replace the removed OSD must be created on the same host as the OSD that was removed.
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 :ref:OSDSpecs <drivegroups> for OSD deployment, your newly added drives will be assigned
the OSD IDs of their replaced counterparts. This assumes that the new drives
still match the OSDSpecs.
Use the --dry-run flag to ensure that the ceph orch apply osd
command will do what you intend. The --dry-run flag shows what the
outcome of the command will be without executing any changes. 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 an OSDSpec file:
.. prompt:: bash #
ceph orch apply -i <osd_spec_file> --dry-run
Expected output:
.. code-block:: console
NAME HOST DATA DB WAL <name_of_osd_spec> node1 /dev/vdb - -
When this output reflects your intent, omit the --dry-run flag to
execute the deployment.
Erase (zap) a device so that it can be reused. zap calls ceph-volume zap on the remote host.
.. prompt:: bash #
ceph orch device zap <hostname> <path>
Example command:
.. prompt:: bash #
ceph orch device zap my_hostname /dev/sdx
.. note::
If the unmanaged flag is not set, cephadm automatically deploys drives that
match the OSDSpec. For example, if you specify the
all-available-devices option when creating OSDs, when you zap a
device the cephadm orchestrator automatically creates a new OSD on the
device. To disable this behavior, see :ref:cephadm-osd-declarative.
.. _osd_autotune:
OSD daemons will adjust their memory consumption based on the
:confval:osd_memory_target config option. If Ceph is deployed
on dedicated nodes that are not sharing
memory with other services, cephadm will automatically adjust the per-OSD
memory consumption target based on the total amount of RAM and the number of deployed
OSDs. This allows the full use of available memory, and adapts when OSDs or
RAM are added or removed.
.. warning:: Cephadm sets :confval:osd_memory_target_autotune to true by
default which is usually not appropriate for converged architectures, where
a given node is used for both Ceph and compute purposes.
Cephadm will use a fraction
:confval:mgr/cephadm/autotune_memory_target_ratio of available memory,
subtracting memory consumed by non-autotuned daemons (non-OSDs and OSDs for which
:confval:osd_memory_target_autotune is false), and then divide the
balance by the number of OSDs.
The final targets are reflected in the config database with options like the below:
.. code-block:: console
WHO MASK LEVEL OPTION VALUE osd host:foo basic osd_memory_target 126092301926 osd host:bar basic osd_memory_target 6442450944
Both the limits and the current memory consumed by each daemon are visible from
the ceph orch ps output in the MEM LIMIT column:
.. code-block:: console
NAME HOST PORTS STATUS REFRESHED AGE MEM USED MEM LIMIT VERSION IMAGE ID CONTAINER ID
osd.1 dael running (3h) 10s ago 3h 72857k 117.4G 17.0.0-3781-gafaed750 7015fda3cd67 9e183363d39c
osd.2 dael running (81m) 10s ago 81m 63989k 117.4G 17.0.0-3781-gafaed750 7015fda3cd67 1f0cc479b051
osd.3 dael running (62m) 10s ago 62m 64071k 117.4G 17.0.0-3781-gafaed750 7015fda3cd67 ac5537492f27
To exclude an OSD from memory autotuning, disable the autotune option
for that OSD and also set a specific memory target. For example,
.. prompt:: bash #
ceph config set osd.123 osd_memory_target_autotune false ceph config set osd.123 osd_memory_target 16G
.. _drivegroups:
:ref:orchestrator-cli-service-spec\s of type osd provide a way to use the
properties of drives to describe a Ceph cluster's layout. Service specifications
are an abstraction used to tell Ceph which drives to transform into OSDs
and which configurations to apply to those OSDs.
:ref:orchestrator-cli-service-spec\s make it possible to target drives
for transformation into OSDs even when the Ceph cluster operator does not know
the specific device names and paths associated with those disks.
:ref:orchestrator-cli-service-spec\s make it possible to define a YAML
or JSON file that can be used to reduce the amount of manual work involved
in creating OSDs.
.. note::
We recommend that advanced OSD specs include the service_id field.
OSDs created using ceph orch daemon add or ceph orch apply osd --all-available-devices are placed in the plain osd service. Failing
to include a service_id in your OSD spec causes the Ceph cluster to mix
the OSDs from your spec with those OSDs, which can potentially result in the
overwriting of service specs created by cephadm to track them. Newer
versions of cephadm block OSD specs that
do not include the service_id.
For example, instead of running the following command:
.. prompt:: bash [monitor.1]#
ceph orch daemon add osd <host>:<path-to-device>
for each device and each host, we can create a .yaml or .json file that
allows us to describe the layout. Here is the most basic example:
Create a file called (for example) osd_spec.yml:
.. code-block:: yaml
service_type: osd
service_id: default_drive_group # custom name of the osd spec
placement:
host_pattern: '*' # which hosts to target
spec:
data_devices: # the type of devices you are applying specs to
all: true # a filter, check below for a full list
This means :
#. Turn any available device (ceph-volume decides which are available) into an
OSD on all hosts that match the glob pattern '*'. The glob pattern matches
registered hosts from ceph orch host ls. See
:ref:cephadm-services-placement-by-pattern-matching for more on using
host_pattern matching to use devices for OSDs.
#. Pass osd_spec.yml to osd create by using the following command:
.. prompt:: bash [monitor.1]#
ceph orch apply -i /path/to/osd_spec.yml
This specification is applied to all the matching hosts to deploy OSDs.
Strategies more complex than the one specified by the all filter are
possible. See :ref:osd_filters for details.
A --dry-run flag can be passed to the apply osd command to display a
synopsis of the proposed layout.
Example
.. prompt:: bash [monitor.1]#
ceph orch apply -i /path/to/osd_spec.yml --dry-run
.. _osd_filters:
.. note::
Filters are applied using an AND operation by default. This means that a drive
must match all filter criteria to be selected. This behavior can
be adjusted by setting filter_logic: OR in the OSD specification.
Filters are used to select sets of drives for OSD data or WAL+DB offload based
on various attributes. These attributes are gathered by ceph-volume's drive
inventory. Retrieve these attributes with this command:
.. prompt:: bash #
ceph-volume inventory </path/to/drive>
Vendor or Model ^^^^^^^^^^^^^^^
Specific drives can be targeted by vendor brand, manufacturer) or model (SKU):
.. code-block:: yaml
model: drive_model_name
or
.. code-block:: yaml
vendor: drive_vendor_name
Size ^^^^
Specific drive capacities can be targeted with size:
.. code-block:: yaml
size: size_spec
Size specs
Size specifications can be of the following forms:
We explore examples below.
To match only drives of an exact capacity:
.. code-block:: yaml
size: '10T'
Note that drive capacity is often not an exact multiple of units, so it is often best practice to match drives within a range of sizes as shown below. This handles future drives of the same class that may be of a different model and thus slightly different in size. Or say you have 10 TB drives today but may add 16 TB drives next year:
.. code-block:: yaml
size: '10T:40T'
To match only drives that are less than or equal to 1701 GB in size:
.. code-block:: yaml
size: ':1701G'
To include drives equal to or greater than 666 GB in size:
.. code-block:: yaml
size: '666G:'
The supported units of size are Megabyte (M), Gigabyte (G) and Terabyte (T).
The B (byte) suffix for units is also acceptable: MB, GB, TB.
Rotational ^^^^^^^^^^
This gates based on the 'rotational' attribute of each drive, as indicated by the kernel. This attribute is usually as expected for bare HDDs and SSDs installed in each node. Exotic or layered device presentations may however be reported differently than you might expect or desire:
dCache, Bcache, OpenCAS, etc.In such cases you may align the kernel's reporting with your expectations
by adding a udev rule to override the default behavior. The below rule
was used for this purpose to override the rotational attribute on OSD
nodes with no local physical drives and only attached SAN LUNs. It is not
intended for deployment in all scenarios; you will have to determine what is
right for your systems. If by emplacing such a rule you summon eldritch horrors
from beyond spacetime, that's on you.
.. code-block:: none
ACTION=="add|change", KERNEL=="sd[a-z]*", ATTR{queue/rotational}="0"
ACTION=="add|change", KERNEL=="dm*", ATTR{queue/rotational}="0"
ACTION=="add|change", KERNEL=="nbd*", ATTR{queue/rotational}="0"
Spec file syntax:
.. code-block:: yaml
rotational: 0 | 1
1 to match all drives that the kernel indicates are rotational
0 to match all drives that are non-rotational (SATA, SATA, NVMe SSDs, SAN LUNs, etc)
All ^^^
This matches all drives that are available, i.e. they are free of partitions, GPT labels, etc.
.. note:: This may only be specified for data_devices.
.. code-block:: yaml
all: true
Limiter ^^^^^^^
If filters are specified but you wish to limit the number of drives that they
match, use the limit attribute. This is useful when one uses some
drives for non-Ceph purposes, or when multiple OSD strategies are
intended.
.. code-block:: yaml
limit: 2
For example, when using vendor to match all drives branded VendorA
but you wish to use at most two of them per host as OSDs, specify a limit:
.. code-block:: yaml
data_devices:
vendor: VendorA
limit: 2
.. note:: limit is usually appropriate in only certain specific scenarios.
There are multiple optional settings that specify the way OSDs are deployed. Add these options to an OSD spec for them to take effect.
This example deploys encrypted OSDs on all unused drives. Note that if Linux
MD mirroring is used for the boot, /var/log, or other volumes this spec may
grab replacement or added drives before you can employ them for non-OSD purposes.
The unmanaged attribute may be set to pause automatic deployment until you
are ready.
.. code-block:: yaml
service_type: osd
service_id: example_osd_spec
placement:
host_pattern: '*'
spec:
data_devices:
all: true
encrypted: true
Ceph Squid onwards support TPM2 token enrollment for LUKS2 devices.
Add the tpm2 attribute to the OSD spec:
.. code-block:: yaml
service_type: osd
service_id: example_osd_spec_with_tpm2
placement:
host_pattern: '*'
spec:
data_devices:
all: true
encrypted: true
tpm2: true
A full list of supported attributes:
.. py:currentmodule:: ceph.deployment.drive_group
.. autoclass:: DriveGroupSpec :members: :exclude-members: from_json
When all cluster nodes have identical drives and we wish to use them all as OSDs with offloaded WAL+DB:
.. code-block:: none
10 HDDs
Vendor: VendorA
Model: HDD-123-foo
Size: 4TB
2 SAS/SATA SSDs
Vendor: VendorB
Model: MC-55-44-ZX
Size: 512GB
This is a common arrangement and can be described easily:
.. code-block:: yaml
service_type: osd
service_id: osd_spec_default
placement:
host_pattern: '*'
spec:
data_devices:
model: HDD-123-foo # Note, HDD-123 would also be valid
db_devices:
model: MC-55-44-XZ # Same here, MC-55-44 is valid
However, we can improve the OSD specification by filtering based on properties of the drives instead of specific models, as models may change over time as drives are replaced or added:
.. code-block:: yaml
service_type: osd
service_id: osd_spec_default
placement:
host_pattern: '*'
spec:
data_devices:
rotational: 1 # The kernel flags as HDD
db_devices:
rotational: 0 # The kernel flags as SSD (SAS/SATA/NVMe)
Here designate all HDDs to be data devices (OSDs) and all SSDs to be used for WAL+DB offload.
If you know that drives larger than 2 TB should always be used as data devices, and drives smaller than 2 TB should always be used as WAL/DB devices, you can filter by size:
.. code-block:: yaml
service_type: osd
service_id: osd_spec_default
placement:
host_pattern: '*'
spec:
data_devices:
size: '2TB:' # Drives larger than 2 TB
db_devices:
size: ':2TB' # Drives smaller than 2TB
.. note:: All of the above OSD specs are equally valid. Which you use depends on taste and on how much you expect your node layout to change.
Here we specify two distinct strategies for deploying OSDs across multiple types of media, usually for use by separate pools:
.. code-block:: none
10 HDDs
Vendor: VendorA
Model: HDD-123-foo
Size: 4TB
12 SAS/SATA SSDs
Vendor: VendorB
Model: MC-55-44-ZX
Size: 512GB
2 NVME SSDs
Vendor: VendorC
Model: NVME-QQQQ-987
Size: 256GB
This can be specificed with two service specs in the same file:
.. code-block:: yaml
service_type: osd
service_id: osd_spec_hdd
placement:
host_pattern: '*'
spec:
data_devices: # Select all drives the kernel identifies as HDDs
rotational: 1 # for OSD data
db_devices:
model: MC-55-44-XZ # Select only this model for WAL+DB offload
limit: 2 # Select at most two for this purpose
db_slots: 5 # Chop the DB device into this many slices and
# use one for each of this many HDD OSDs
---
service_type: osd
service_id: osd_spec_ssd # Unique so it doesn't overwrite the above
placement:
host_pattern: '*'
spec: # This scenario is uncommon
data_devices:
model: MC-55-44-XZ # Select drives of this model for OSD data
db_devices: # Select drives of this brand for WAL+DB. Since the
vendor: VendorC # data devices are SAS/SATA SSDs this would make sense for NVMe SSDs
db_slots: 2 # Back two slower SAS/SATA SSD data devices with each NVMe slice
This would create the desired layout by using all HDDs as data devices with two
SATA/SAS SSDs assigned as dedicated DB/WAL devices, each backing five HDD OSDs.
The remaining ten SAS/SATA SSDs will be
used as OSD data devices, with VendorC NVMEs SSDs assigned as
dedicated DB/WAL devices, each serving two SAS/SATA OSDs. We call these _hybrid OSDs.
When a cluster comprises hosts with different drive layouts, or a complex constellation of multiple media types, it is recommended to apply multiple OSD specs, each matching only one set of hosts. Typically you will have a single spec for each type of host.
The service_id must be unique: if a new OSD spec with an already
applied service_id is applied, the existing OSD spec will be superseded.
Cephadm will then create new OSD daemons on unused drives based on the new spec
definition. Existing OSD daemons will not be affected. See :ref:cephadm-osd-declarative.
Example:
Nodes 1-5:
.. code-block:: none
20 HDDs
Vendor: VendorA
Model: SSD-123-foo
Size: 4TB
2 SSDs
Vendor: VendorB
Model: MC-55-44-ZX
Size: 512GB
Nodes 6-10:
.. code-block:: none
5 NVMEs
Vendor: VendorA
Model: SSD-123-foo
Size: 4TB
20 SSDs
Vendor: VendorB
Model: MC-55-44-ZX
Size: 512GB
You can specify a placement to target only certain nodes.
.. code-block:: yaml
service_type: osd
service_id: disk_layout_a
placement:
label: disk_layout_a
spec:
data_devices:
rotational: 1 # All drives identified as HDDs
db_devices:
rotational: 0 # All drives identified as SSDs
---
service_type: osd
service_id: disk_layout_b
placement:
label: disk_layout_b
spec:
data_devices:
model: MC-55-44-XZ # Only this model
db_devices:
model: SSD-123-foo # Only this model
This applies different OSD specs to different hosts that match hosts
tagged with ceph orch labels via the placement filter.
For more information, see :ref:orchestrator-cli-placement-spec.
.. note::
Assuming each host has a unique disk layout, each OSD
spec must have a unique ``service_id``.
All previous cases colocated the WALs with the DBs. It is however possible to deploy the WAL on a separate device if desired.
.. code-block:: none
20 HDDs
Vendor: VendorA
Model: SSD-123-foo
Size: 4TB
2 SAS/SATA SSDs
Vendor: VendorB
Model: MC-55-44-ZX
Size: 512GB
2 NVME SSDs
Vendor: VendorC
Model: NVME-QQQQ-987
Size: 256GB
The OSD spec for this case would look like the following, using the model filter:
.. code-block:: yaml
service_type: osd
service_id: osd_spec_default
placement:
host_pattern: '*'
spec:
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 device paths as below, when every matched host is expected to present devices identically.
.. code-block:: yaml
service_type: osd
service_id: osd_using_paths
placement:
hosts:
- node01
- node02
spec:
data_devices:
paths:
- /dev/sdb
db_devices:
paths:
- /dev/sdc
wal_devices:
paths:
- /dev/sdd
In most cases it is preferable to accomplish this with other filters
including size or vendor so that OSD services adapt when
Linux or an HBA may enumerate devices differently across boots, or when
drives are added or replaced.
It is possible to specify a crush_device_class parameter
to be applied to OSDs created on devices matched by the paths filter:
.. code-block:: yaml
service_type: osd
service_id: osd_using_paths
placement:
hosts:
- node01
- node02
crush_device_class: ssd
spec:
data_devices:
paths:
- /dev/sdb
- /dev/sdc
db_devices:
paths:
- /dev/sdd
wal_devices:
paths:
- /dev/sde
The crush_device_class attribute may be specified at OSD granularity
via the paths keyword with the following syntax:
.. code-block:: yaml
service_type: osd
service_id: osd_using_paths
placement:
hosts:
- node01
- node02
crush_device_class: ssd
spec:
data_devices:
paths:
- path: /dev/sdb
crush_device_class: ssd
- path: /dev/sdc
crush_device_class: nvme
db_devices:
paths:
- /dev/sdd
wal_devices:
paths:
- /dev/sde
.. _cephadm-osd-activate:
If a host's operating system has been reinstalled, existing OSDs
must be activated again. cephadm provides a wrapper for
:ref:ceph-volume-lvm-activate that activates all existing OSDs on a host.
The following procedure explains how to use cephadm to activate OSDs on a
host that has had its operating system reinstalled.
This example applies to two hosts: ceph01 and ceph04.
ceph01 is a host equipped with an admin keyring.ceph04 is the host with the recently reinstalled operating system.#. Install cephadm and podman on the host. The command for installing
these utilities will depend upon the operating system of the host.
#. Retrieve the public key.
.. prompt:: bash ceph01#
cd /tmp ; ceph cephadm get-pub-key > ceph.pub
#. Copy the key (from ceph01) to the freshly reinstalled host (ceph04):
.. prompt:: bash ceph01#
ssh-copy-id -f -i ceph.pub root@<hostname>
#. Retrieve the private key in order to test the connection:
.. prompt:: bash ceph01#
cd /tmp ; ceph config-key get mgr/cephadm/ssh_identity_key > ceph-private.key
#. From ceph01, modify the permissions of ceph-private.key:
.. prompt:: bash ceph01#
chmod 400 ceph-private.key
#. Log in to ceph04 from ceph01 to test the connection and
configuration:
.. prompt:: bash ceph01#
ssh -i /tmp/ceph-private.key ceph04
#. While logged into ceph01, remove ceph.pub and ceph-private.key:
.. prompt:: bash ceph01#
cd /tmp ; rm ceph.pub ceph-private.key
#. If you run your own container registry, instruct the orchestrator to log into it on each host:
.. prompt:: bash #
ceph cephadm registry-login my-registry.domain <user> <password>
When the orchestrator performs the registry login, it will attempt to deploy
any missing daemons to the host. This includes crash, node-exporter,
and any other daemons that the host ran before its operating system was
reinstalled.
To be clea: cephadm attempts to deploy missing daemons to all
hosts managed by cephadm, when cephadm
determines that the hosts are online. In this context, "online" means
"present in the output of the ceph orch host ls command and with a
status that is not offline or maintenance. If it is necessary to log
in to the registry in order to pull the images for the missing daemons, then
deployment of the missing daemons will fail until the process of logging
in to the registry has been completed.
.. note:: This step is not necessary if you do not run your own container
registry. If your host is still in the "host list", which can be
retrieved by running the command ceph orch host ls, you do not
need to run this command.
#. Activate the OSDs on the host that has recently had its operating system reinstalled:
.. prompt:: bash #
ceph cephadm osd activate ceph04
This command causes cephadm to scan all existing disks for OSDs. This
command will make cephadm deploy any missing daemons to the host
specified.
This procedure was developed by Eugen Block in Feburary of 2025, and a blog
post pertinent to its development can be seen here:
Eugen Block's "Cephadm: Activate existing OSDs" blog post <https://heiterbiswolkig.blogs.nde.ag/2025/02/06/cephadm-activate-existing-osds/>_.
.. note::
It is usually not safe to run ceph orch restart osd.myosdservice on a
running cluster, as attention is not paid to CRUSH failure domains, and
parallel OSD restarts may lead to temporary data unavailability or in rare
cases even data loss.
ceph-volumerados-index