Pre-configuring Ceph

This article uses the terms "nodes" and "cluster" to refer to Ceph servers. These terms do not refer to VMmanager nodes and clusters.

Before connecting Ceph storage to the VMmanager cluster, you should pre-configure the Ceph cluster nodes. This article provides general information about the installation. It is recommended that you create a Ceph cluster according to the official documentation.

Before creating a cluster, make sure that the equipment used matches the system requirements. It is recommended using Ceph software version no older than 13.2.0.

Requirements for cluster nodes

The following physical or virtual servers should be part of the cluster:

• data server (OSD);
• at least three monitor servers (MON);
• administrative server (ADM);
• monitoring service (MGR);
• metadata server (MDS). It is necessary if you use the CephFS file system.

Servers must meet the following requirements:

1. A server with VMmanager platform cannot be used as a cluster node.
2. It is not recommended to use nodes of VMmanager cluster. This places high load on the server and complicates the recovery process in the event of a failure.
3. It is recommended using servers that are in the same rack and the same network segment.
4. It is recommended using a high-speed network connection between cluster nodes.
5. One operating system must be installed on all servers.
6. Port 6789/TCP should be available on the monitor servers; and ports 6800 to 7300/TCP should be available on the data servers.
7. All nodes in the cluster must have an unmounted partition or disk to install the Ceph software.

Example of cluster node preparation

The example describes how to create a cluster using servers:

1. ceph-cluster-1 with IP address 172.31.245.51. Designation — MON, OSD, ADM, MGR.
2. ceph-cluster-2 with IP address 172.31.246.77. Designation — MON, OSD.
3. ceph-cluster-3 with IP address 172.31.246.82. Designation — MON, OSD.

 If the error "RuntimeError: NoSectionError: No section: 'ceph'" occurs while executing the ceph-deploy command, rerun the command.

All servers

1. Install Ceph software:
   

   1. Execute the command:

      yum install -y https://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm

      CODE

   2. Create the file /etc/yum.repos.d/ceph.repo and add the following lines to it:

      [ceph-noarch]
      name=Ceph noarch packages
      baseurl=https://download.ceph.com/rpm-nautilus/el7/noarch
      enabled=1
      gpgcheck=1
      type=rpm-md
      gpgkey=https://download.ceph.com/keys/release.asc

      CODE

   3. Execute the command:

      yum update

      CODE

2.  Install software to run NTP. This will prevent problems arising from the system time shift.

   yum install ntp ntpdate ntp-doc

   CODE

3. Create a ceph user and set the necessary permissions:

   useradd -d /home/ceph -m ceph
   passwd ceph
   echo "ceph ALL = (root) NOPASSWD:ALL" | sudo tee /etc/sudoers.d/ceph
   chmod 0440 /etc/sudoers.d/ceph

   CODE

4. Create aliases for cluster nodes in /etc/hosts:

   172.31.245.51 ceph1.example.com ceph1
   172.31.246.77 ceph2.example.com ceph2
   172.31.246.82 ceph3.example.com ceph3

   CODE

5. Add Ceph services to firewalld settings:

   firewall-cmd --zone=public --add-service=ceph-mon --permanent
   firewall-cmd --zone=public --add-service=ceph --permanent
   firewall-cmd --reload

   CODE

Administrative server

1. Install the ceph-deploy and python-setuptools packages:

   yum install ceph-deploy python-setuptools

   CODE

2. Create ssh keys and copy them to all nodes of the cluster:

   ssh-keygen
   ssh-copy-id ceph@ceph1
   ssh-copy-id ceph@ceph2
   ssh-copy-id ceph@ceph3

   CODE

3. Add lines to the file ~/.ssh/config:

   Host ceph1
   Hostname ceph1
   User ceph
   Host ceph2
   Hostname ceph2
   User ceph
   Host ceph3
   Hostname ceph3
   User ceph

   CODE

4. Create my-cluster directory for configuration and ceph-deploy files and enter to that directory:

   mkdir my-cluster
   cd my-cluster

   CODE

5. Create the cluster configuration file:

   ceph-deploy new ceph1 ceph2 ceph3

   CODE
    Where

   ceph1 ceph2 ceph3 — cluster nodes that are monitor servers

   When using Ceph Storage with one cluster node replace the value of "osd_crush_chooseleaf_type" in configuration ceph.conf with 0.

6. Add information about the cluster node network to the ceph.conf configuration file: 

   echo "public_network = 172.31.240.0/20" >> ceph.conf

   CODE

7. Install ceph-deploy on cluster codes:

   ceph-deploy install ceph1 ceph2 ceph3

   CODE

8. Deploy a monitoring service:

   ceph-deploy mgr create ceph1

   CODE

9. Create and initialize the monitor servers:

   ceph-deploy mon create-initial

   CODE

10. Copy the configuration files to the cluster nodes:

    ceph-deploy admin ceph1 ceph2 ceph3

    CODE

11. Add data servers to the cluster:

    ceph-deploy osd create --data /dev/sdb ceph1
    ceph-deploy osd create --data /dev/sdb ceph2
    ceph-deploy osd create --data /dev/sdb ceph3

    CODE
     Where

    /dev/sdb — storage device on the cluster node

12. Erase /dev/sdb drives on data servers:

    ceph-deploy disk zap ceph1:sdb ceph2:sdb ceph3:sdb 

    BASH

Useful tips

Related topics:

• Creating a cluster
• Managing cluster storages
• Creating an RBD storage