Chapter 9. Management of MDS service using the Ceph Orchestrator As a storage administrator, you can use Ceph Orchestrator with Cephadm in the backend to deploy the MDS service. By default, a Ceph File System (CephFS) uses only one active MDS daemon. However, systems with many clients benefit from multiple active MDS daemons. This section covers the following administrative tasks: Deploying the MDS service using the command line interface . Deploying the MDS service using the service specification . Removing the MDS service using the Ceph Orchestrator . 9.1. Prerequisites A running Red Hat Ceph Storage cluster. Root-level access to all the nodes. Hosts are added to the cluster. All manager, monitor and OSD daemons are deployed. 9.2. Deploying the MDS service using the command line interface Using the Ceph Orchestrator, you can deploy the Metadata Server (MDS) service using the placement specification in the command line interface. Ceph File System (CephFS) requires one or more MDS. Note Ensure you have at least two pools, one for Ceph file system (CephFS) data and one for CephFS metadata. Prerequisites A running Red Hat Ceph Storage cluster. Hosts are added to the cluster. All manager, monitor, and OSD daemons are deployed. Procedure Log into the Cephadm shell: Example There are two ways of deploying MDS daemons using placement specification: Method 1 Use ceph fs volume to create the MDS daemons. This creates the CephFS volume and pools associated with the CephFS, and also starts the MDS service on the hosts. Syntax Note By default, replicated pools are created for this command. Example Method 2 Create the pools, CephFS, and then deploy MDS service using placement specification: Create the pools for CephFS: Syntax Example Typically, the metadata pool can start with a conservative number of Placement Groups (PGs) as it generally has far fewer objects than the data pool. It is possible to increase the number of PGs if needed. The pool sizes range from 64 PGs to 512 PGs. Size the data pool is proportional to the number and sizes of files you expect in the file system. Important For the metadata pool, consider to use: A higher replication level because any data loss to this pool can make the whole file system inaccessible. Storage with lower latency such as Solid-State Drive (SSD) disks because this directly affects the observed latency of file system operations on clients. Create the file system for the data pools and metadata pools: Syntax Example Deploy MDS service using the ceph orch apply command: Syntax Example Verification List the service: Example Check the CephFS status: Example List the hosts, daemons, and processes: Syntax Example Additional Resources See the Red Hat Ceph Storage File System Guide for more information about creating the Ceph File System (CephFS). For information on pools, see Pools . 9.3. Deploying the MDS service using the service specification Using the Ceph Orchestrator, you can deploy the MDS service using the service specification. Note Ensure you have at least two pools, one for the Ceph File System (CephFS) data and one for the CephFS metadata. Prerequisites A running Red Hat Ceph Storage cluster. Hosts are added to the cluster. All manager, monitor, and OSD daemons are deployed. Procedure Create the mds.yaml file: Example Edit the mds.yaml file to include the following details: Syntax Example Mount the YAML file under a directory in the container: Example Navigate to the directory: Example Log into the Cephadm shell: Example Navigate to the following directory: Example Deploy MDS service using service specification: Syntax Example Once the MDS services is deployed and functional, create the CephFS: Syntax Example Verification List the service: Example List the hosts, daemons, and processes: Syntax Example Additional Resources See the Red Hat Ceph Storage File System Guide for more information about creating the Ceph File System (CephFS). 9.4. Removing the MDS service using the Ceph Orchestrator You can remove the service using the ceph orch rm command. Alternatively, you can remove the file system and the associated pools. Prerequisites A running Red Hat Ceph Storage cluster. Root-level access to all the nodes. Hosts are added to the cluster. At least one MDS daemon deployed on the hosts. Procedure There are two ways of removing MDS daemons from the cluster: Method 1 Remove the CephFS volume, associated pools, and the services: Log into the Cephadm shell: Example Set the configuration parameter mon_allow_pool_delete to true : Example Remove the file system: Syntax Example This command will remove the file system, its data, and metadata pools. It also tries to remove the MDS using the enabled ceph-mgr Orchestrator module. Method 2 Use the ceph orch rm command to remove the MDS service from the entire cluster: List the service: Example Remove the service Syntax Example Verification List the hosts, daemons, and processes: Syntax Example Additional Resources See Deploying the MDS service using the command line interface section in the Red Hat Ceph Storage Operations Guide for more information. See Deploying the MDS service using the service specification section in the Red Hat Ceph Storage Operations Guide for more information.

Commands:
cephadm shell
ceph fs volume create FILESYSTEM_NAME --placement=" NUMBER_OF_DAEMONS HOST_NAME_1 HOST_NAME_2 HOST_NAME_3 "
ceph fs volume create test --placement="2 host01 host02"
ceph osd pool create DATA_POOL [ PG_NUM ] ceph osd pool create METADATA_POOL [ PG_NUM ]
ceph osd pool create cephfs_data 64 ceph osd pool create cephfs_metadata 64
ceph fs new FILESYSTEM_NAME METADATA_POOL DATA_POOL
ceph fs new test cephfs_metadata cephfs_data
ceph orch apply mds FILESYSTEM_NAME --placement=" NUMBER_OF_DAEMONS HOST_NAME_1 HOST_NAME_2 HOST_NAME_3 "
ceph orch apply mds test --placement="2 host01 host02"
ceph orch ls
ceph fs ls ceph fs status
ceph orch ps --daemon_type= DAEMON_NAME
ceph orch ps --daemon_type=mds
touch mds.yaml
service_type: mds service_id: FILESYSTEM_NAME placement: hosts: - HOST_NAME_1 - HOST_NAME_2 - HOST_NAME_3
service_type: mds service_id: fs_name placement: hosts: - host01 - host02
cephadm shell --mount mds.yaml:/var/lib/ceph/mds/mds.yaml
cd /var/lib/ceph/mds/
cephadm shell
cd /var/lib/ceph/mds/
ceph orch apply -i FILE_NAME .yaml
ceph orch apply -i mds.yaml
ceph fs new CEPHFS_NAME METADATA_POOL DATA_POOL
ceph fs new test metadata_pool data_pool
ceph orch ls
ceph orch ps --daemon_type= DAEMON_NAME
ceph orch ps --daemon_type=mds
cephadm shell
ceph config set mon mon_allow_pool_delete true
ceph fs volume rm FILESYSTEM_NAME --yes-i-really-mean-it
ceph fs volume rm cephfs-new --yes-i-really-mean-it
ceph orch ls
ceph orch rm SERVICE_NAME
ceph orch rm mds.test
ceph orch ps
ceph orch ps