Notice

This document is for a development version of Ceph.

ZFS

The backend of ceph-volume zfs is ZFS, it relies heavily on the usage of tags, which is a way for ZFS to allow extending its volume metadata. These values can later be queried against devices and it is how they get discovered later.

Currently this interface is only usable when running on FreeBSD.

Warning

These APIs are not meant to be public, but are documented so that it is clear what the tool is doing behind the scenes. Do not alter any of these values.

Tag API

The process of identifying filesystems, volumes and pools as part of Ceph relies on applying tags on all volumes. It follows a naming convention for the namespace that looks like:

ceph.<tag name>=<tag value>

All tags are prefixed by the ceph keyword to claim ownership of that namespace and make it easily identifiable. This is how the OSD ID would be used in the context of zfs tags:

ceph.osd_id=0

Tags on filesystems are stored as property. Tags on a zpool are stored in the comment property as a concatenated list separated by ;

Metadata

The following describes all the metadata from Ceph OSDs that is stored on a ZFS filesystem, volume, pool:

type

Describes if the device is an OSD or Journal, with the ability to expand to other types when supported

Example:

ceph.type=osd

cluster_fsid

Example:

ceph.cluster_fsid=7146B649-AE00-4157-9F5D-1DBFF1D52C26

data_device

Example:

ceph.data_device=/dev/ceph/data-0

data_uuid

Example:

ceph.data_uuid=B76418EB-0024-401C-8955-AE6919D45CC3

journal_device

Example:

ceph.journal_device=/dev/ceph/journal-0

journal_uuid

Example:

ceph.journal_uuid=2070E121-C544-4F40-9571-0B7F35C6CB2B

osd_fsid

Example:

ceph.osd_fsid=88ab9018-f84b-4d62-90b4-ce7c076728ff

osd_id

Example:

ceph.osd_id=1

block_device

Just used on bluestore backends. Captures the path to the logical volume path.

Example:

ceph.block_device=/dev/gpt/block-0

block_uuid

Just used on bluestore backends. Captures either the logical volume UUID or the partition UUID.

Example:

ceph.block_uuid=E5F041BB-AAD4-48A8-B3BF-31F7AFD7D73E

db_device

Just used on bluestore backends. Captures the path to the logical volume path.

Example:

ceph.db_device=/dev/gpt/db-0

db_uuid

Just used on bluestore backends. Captures either the logical volume UUID or the partition UUID.

Example:

ceph.db_uuid=F9D02CF1-31AB-4910-90A3-6A6302375525

wal_device

Just used on bluestore backends. Captures the path to the logical volume path.

Example:

ceph.wal_device=/dev/gpt/wal-0

wal_uuid

Just used on bluestore backends. Captures either the logical volume UUID or the partition UUID.

Example:

ceph.wal_uuid=A58D1C68-0D6E-4CB3-8E99-B261AD47CC39

compression

A compression-enabled device can always be set using the native zfs settings on a volume or filesystem. This will/can be activated during creation of the volume of filesystem. When activated by ceph-volume zfs this tag will be created. Compression manually set AFTER ceph-volume will go unnoticed, unless this tag is also manually set.

Example for an enabled compression device:

ceph.vdo=1