Setting up a Ceph storage platform

Ceph is a free-software storage platform, implements object storage on a single distributed computer cluster, and provides interfaces for object-, block- and file-level storage.

Ceph documentation

Tutorials:

Object storage:

  • Ceph implements distributed object storage. Ceph’s software libraries provide client applications with direct access to the reliable autonomic distributed object store (RADOS) object-based storage system, and also provide a foundation for some of Ceph’s features, including RADOS Block Device (RBD), RADOS Gateway, and the Ceph File System.

Ceph installation

Get an overview of current stable and development versions:

Preflight instructions

First follow the preflight instructions for RHEL/CentOS.

Enable the EPEL repository:

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

Then enable the Ceph repository for the current mimic or luminous release Yum repository:

cat << EOM > /etc/yum.repos.d/ceph.repo
[ceph-noarch]
name=Ceph noarch packages
# baseurl=https://download.ceph.com/rpm-luminous/el7/noarch
baseurl=https://download.ceph.com/rpm-mimic/el7/noarch
enabled=1
gpgcheck=1
type=rpm-md
gpgkey=https://download.ceph.com/keys/release.asc
EOM

The baseurl determines which release you will get.

Install this package:

yum install ceph-deploy

Make sure that NTP is installed and configured:

yum install ntp ntpdate ntp-doc

Install SSH server:

yum install openssh-server
Creating cephuser

Following the tutorial How to build a Ceph Distributed Storage Cluster on CentOS 7 we first create a Ceph user:

export CephUSER=984
groupadd -g $CephUSER cephuser
useradd  -m -c "Ceph storage user" -d /var/lib/cephuser -u $CephUSER -g cephuser  -s /bin/bash cephuser
passwd cephuser

Please do NOT use ceph as the user name.

Firewalld configuration

The Ceph preflight instructs to add ceph-mon and ceph services to firewalld.

Om Monitor nodes:

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

On OSD and MDS nodes:

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

On all nodes then reload the firewalld:

firewall-cmd --reload

Quickstart instructions for RHEL/CentOS

Follow the quickstart instructions for RHEL/CentOS.

You need an admin node which is not one of the Ceph nodes. Log in to the admin node and run these instructions as user cephuser (not as root or by sudo)!

Create a Ceph Storage Cluster with one Ceph Monitor and three Ceph OSD Daemons:

mkdir my-cluster
cd my-cluster

Create the cluster on node mon1:

ceph-deploy new mon1

This will create ceph.conf and other configuration files in the current directory.

Warning:

The ceph-deploy tool will install the old jewel v.10 release by default!

You need to specify the current stable mimic v.13 (or the older luminous v.12) release explicitly, otherwise you will get the old jewel v.10 by default!! See this thread.

Install Ceph on the monitor and OSD nodes:

ceph-deploy install --release mimic mon1 osd1 osd2 osd3

After the installation has been completed, you may verify the Ceph version on all nodes:

cephuser# sudo ceph --version

Deploy the initial monitor(s) and gather the keys:

ceph-deploy mon create-initial

Use ceph-deploy to copy the configuration file and admin key to your admin node and your Ceph Nodes:

ceph-deploy admin mon1 mds1 osd1 osd2 osd3

Deploy a manager daemon on the monitor node (required only for luminous+ builds):

ceph-deploy mgr create mon1

Create data devices (here assuming /dev/sdXX - change this to an unused disk device) on all the OSD nodes:

ceph-deploy osd create --data /dev/sdXX osd1
ceph-deploy osd create --data /dev/sdXX osd2
ceph-deploy osd create --data /dev/sdXX osd3

Check the health details:

ceph health detail

The correct result would be:

HEALTH_OK

Test the Ceph cluster

Do the Exercise: Locate an Object section at the end of the quickstart page. Remember that all commands must be preceded by sudo.

At the end of the exercise the storage pool is removed, however, this is not permitted with the mimic release. The following error is printed:

Error EPERM: pool deletion is disabled; you must first set the mon_allow_pool_delete config option to true before you can destroy a pool

Configure Ceph with Ansible

Instructions are in the ceph-ansible page. onsult the Ceph_releases page for Check out the master branch:

git clone https://github.com/ceph/ceph-ansible.git
git checkout masteronsult the Ceph_releases_ page for

Install Ansible:

yum install ansible

See also our Wiki page Ansible_configuration.

Ceph Filesystem (CephFS)

The CephFS filesystem (Ceph FS) is a POSIX-compliant filesystem that uses a Ceph Storage Cluster to store its data. The Ceph filesystem uses the same Ceph Storage Cluster system as Ceph Block Devices, Ceph Object Storage with its S3 and Swift APIs, or native bindings (librados).

See the CephFS_best_practices for recommendations for best results when deploying CephFS. For RHEL/CentOS 7 with kernel 3.10 the following recommendation of the FUSE client applies:

As a rough guide, as of Ceph 10.x (Jewel), you should be using a least a 4.x kernel.
If you absolutely have to use an older kernel, you should use the fuse client instead of the kernel client.

For a configuration guide for CephFS, please see the CephFS instructions.

Create a Ceph filesystem

See the createfs page.

First create two RADOS pools:

ceph osd pool create cephfs_data 128
ceph osd pool create cephfs_metadata 128

The number of placement-groups (PG) is 128 in this example, as appropriate for <5 OSDs, see the placement-groups page.

An erasure-code pool may alternatively be created on 3 or more OSD hosts, in this case one also needs (see createfs):

ceph osd pool set my_ec_pool allow_ec_overwrites true

List the RADOS pools by:

ceph osd lspools

Create a filesystem by:

ceph fs new cephfs cephfs_metadata cephfs_data
ceph fs ls

Show the metadata server mds1 status:

ceph mds stat

To check a cluster’s data usage and data distribution among pools, you can use the df option on the monitoring node:

ceph df

Mount CephFS using FUSE

Installation of ceph-fuse package seems to be undocumented. The CephFS client host must first install some prerequisites:

  1. Enable the EPEL repository as shown above for preflight.
  2. Copy the file /etc/yum.repos.d/ceph.repo to the client host to enable the Ceph repository.

Then install the FUSE package:

yum clean all
yum install ceph-fuse

FUSE documentation is in http://docs.ceph.com/docs/mimic/cephfs/fuse/

Copy the Ceph config and client keyring files from the monitor node (mon1):

client# mkdir /etc/ceph
mon1# cd /etc/ceph; scp ceph.conf ceph.client.admin.keyring client:/etc/ceph/

Do not give extra permissions to the secret ceph.client.admin.keyring file!

Mounting on the client host in /u/cephfs:

mkdir /u/cephfs
ceph-fuse /u/cephfs

The FUSE server is read from ceph.conf, or may be specified explicitly by the option -m mon1:6789 See http://docs.ceph.com/docs/master/man/8/ceph-fuse/

List all mounted FUSE filesystems by:

findmnt -t fuse.ceph-fuse

Umount the filesystem by:

fusermount -u /u/cephfs
Mount by fstab

The FUSE mount can be added to /etc/fstab as follows:

Add a FUSE mount point to fstab like this example:

none    /u/cephfs  fuse.ceph ceph.conf=/etc/ceph/ceph.conf,_netdev,defaults  0 0

Now you can mount the filesystem manually:

mount /u/fstab

Start and enable Systemd services for the /u/cephfs mount point:

systemctl start ceph-fuse@/u/cephfs.service
systemctl enable ceph-fuse@/u/cephfs.service

IT-wiki: Ceph_storage (last edited 2018-06-05 14:19:45 by OleHolmNielsen)