This is a multi-part article where in a series of article we will learn about Gluster File System in Linux, below are the topics we will cover:
- What is GlusterFS?
- Types of Volumes supported with GlusterFS
- Install and Configure GlusterFS Distributed Volume with RHEL/CentOS 8
- Install and Configure GlusterFS Replicated Volume with RHEL/CentOS 8
- Install and Configure GlusterFS Distributed Replicated Volume with RHEL/CentOS 8
Lab Environment
I have create two Virtual Machines using Oracle VirtualBox which is installed on a Linux Server. These two VMs are installed with CentOS 8. Below are the configuration spec of these two virtual machines:
Configuration | Node 1 | Node 2 | Node3 |
---|---|---|---|
Hostname/FQDN | glusterfs-1.example.com | glusterfs-2.example.com | glusterfs-3.example.com |
OS | CentOS 8 | CentOS 8 | CentOS 8 |
IP Address | 10.10.10.6 | 10.10.10.12 | 10.10.10.13 |
Storage 1 (/dev/sda) | 20GB | 20GB | 20GB |
Storage 2 (/dev/sdb) | 10GB | 10GB | 10GB |
Name Resolution
You must configure DNS to resolve hostname or alternatively use /etc/hosts
file. I have updated /etc/hosts
file with the IPs of my GlusterFS nodes
# cat /etc/hosts 127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4 ::1 localhost localhost.localdomain localhost6 localhost6.localdomain6 10.10.10.6 glusterfs-1 glusterfs-1.example.com 10.10.10.12 glusterfs-2 glusterfs-2.example.com 10.10.10.13 glusterfs-3 glusterfs-3.example.com
Install Gluster File system
Install GlusterFS on CentOS 8
Depending upon your environment you can download the repo file of glusterfs from the official page. I am using internal network on my CentOS 8 virtual machine so there is no internet connectivity in my VM which is why I downloaded the glusterfs repo on one of my RHEL 8 node and then created an offline repo by downloading the entire repository
Enable PowerTools repo
You must also enable PowerTools repo or else you will get below error while installing glusterfs-server
python3-pyxattr is needed by glusterfs-srver which is provded by powertools repo from centOS 8 so this also needs to be enabled
To enable powertools
you can manually enable the repo using "enabled=1
" param in /etc/yum.repos.d/CentOS-PowerTools.repo
or you can install yum-utils
first
[root@glusterfs-1 ~]# yum -y install yum-utils
and then later using yum-config-manager
you can enable the PowerTools repo
[root@glusterfs-1 ~]# yum-config-manager --enable PowerTools
To list the available repos
[root@glusterfs-1 ~]# yum repolist CentOS-8 - AppStream 5.1 kB/s | 4.3 kB 00:00 CentOS-8 - Base 6.1 kB/s | 3.8 kB 00:00 CentOS-8 - Extras 256 B/s | 1.5 kB 00:06 CentOS-8 - PowerTools 815 kB/s | 2.0 MB 00:02 Extra Packages for Enterprise Linux 8 - x86_64 6.1 kB/s | 7.7 kB 00:01 GlusterFS clustered file-system 2.9 MB/s | 3.0 kB 00:00 repo id repo name status AppStream CentOS-8 - AppStream 5,001 BaseOS CentOS-8 - Base 1,784 PowerTools CentOS-8 - PowerTools 1,499 epel Extra Packages for Enterprise Linux 8 - x86_64 4,541 extras CentOS-8 - Extras 3
You can install glusterfs-server
to install GlusterFS
[root@glusterfs-1 ~]# rpm -Uvh https://buildlogs.centos.org/centos/8/storage/x86_64/gluster-9/Packages/g/glusterfs-server-9.4-1.el8.x86_64.rpm
Install GlusterFS on Red Hat 8 (RHEL 8)
There are various source and methods to install GlusterFS in RHEL 8
- To install Red Hat Gluster Storage 3.4 using ISO
- To install Red Hat Gluster Storage 3.4 using Subscription Manager
Next to install Red Hat Gluster Storage using redhat-storage-server
rpm
# yum install redhat-storage-server
Start glusterd service
Next start the glusterd service on both the cluster nodes
[root@glusterfs-1 ~]# systemctl start glusterd
Verify the status of the service and make sure it is in active running state:
[root@glusterfs-1 ~]# systemctl status glusterd
● glusterd.service - GlusterFS, a clustered file-system server
Loaded: loaded (/usr/lib/systemd/system/glusterd.service; disabled; vendor preset: disabled)
Active: active (running) since Sun 2020-01-26 02:19:31 IST; 4s ago
Docs: man:glusterd(8)
Process: 2855 ExecStart=/usr/sbin/glusterd -p /var/run/glusterd.pid --log-level $LOG_LEVEL $GLUSTERD_OPTIONS (code=exited, status=0/SUCCESS)
Main PID: 2856 (glusterd)
Tasks: 9 (limit: 26213)
Memory: 3.9M
CGroup: /system.slice/glusterd.service
└─2856 /usr/sbin/glusterd -p /var/run/glusterd.pid --log-level INFO
Jan 26 02:19:31 glusterfs-1.example.com systemd[1]: Starting GlusterFS, a clustered file-system server...
Jan 26 02:19:31 glusterfs-1.example.com systemd[1]: Started GlusterFS, a clustered file-system server.
Enable the service so that the service comes up automatically
[root@glusterfs-1 ~]# systemctl enable glusterd
Create Partition
If you already have an additional logical volume for Gluster File System then you can ignore these steps.
We will create a new logical volume on both our CentOS 8 nodes to create a GlusterFS replicated volume. Now since I have already explained the steps required to create a partition, I won't explain these commands again here.
[root@glusterfs-1 ~]# pvcreate /dev/sdb <-- To create physical volume [root@glusterfs-1 ~]# vgextend rhel /dev/sdb <-- Extend my existing volume group [root@glusterfs-1 ~]# lvcreate -L 2G -n brick1 rhel <-- Create logical volume named "brick1" with size 2GB using rhel VG [root@glusterfs-1 ~]# mkfs.xfs /dev/mapper/rhel-brick1 <-- Format the logical volume using XFS File System
Create a mount point for this new logical volume
[root@glusterfs-3 ~]# mkdir -p /bricks/brick1
Mount the logical volume on this mount point
[root@glusterfs-3 ~]# mount /dev/mapper/rhel-brick1 /bricks/brick1
Verify the same
[root@glusterfs-1 ~]# df -Th /bricks/brick1
Filesystem Type Size Used Avail Use% Mounted on
/dev/mapper/rhel-brick1 xfs 2.0G 47M 2.0G 3% /bricks/brick1
Similarly we will create /dev/mapper/rhel-brick2 on gcluster-2 and /dev/mapper/rhel-brick3 on gcluster-3 node
[root@glusterfs-2 ~]# df -Th /bricks/brick2 Filesystem Type Size Used Avail Use% Mounted on /dev/mapper/rhel-brick2 xfs 2.0G 47M 2.0G 3% /bricks/brick2 [root@glusterfs-3 ~]# df -Th /bricks/brick3 Filesystem Type Size Used Avail Use% Mounted on /dev/mapper/rhel-brick3 xfs 2.0G 47M 2.0G 3% /bricks/brick3
/etc/fstab
of these logical volume on the respective cluster nodes to make sure these gluster file systems gets mounted post reboot
Configure Firewall
Enable port for glusterd service to use GlusterFS Replicated Volume on both the cluster nodes
# firewall-cmd --permanent --add-service=glusterfs # firewall-cmd --reload
Add your nodes to the Trusted Storage Pool (TSP)
Let’s select one host (it doesn’t matter which one); we are going to start our cluster.
We are going to do the following from this one server:
- Add peers to our cluster
- Create a GlusterFS replicated volume
To add our peers to the cluster, we issue the following:
[root@glusterfs-1 ~]# gluster peer probe glusterfs-3.example.com peer probe: success. [root@glusterfs-1 ~]# gluster peer probe glusterfs-2.example.com peer probe: success.
To check the connected peer status
[root@glusterfs-1 ~]# gluster peer status
Number of Peers: 2
Hostname: glusterfs-3.example.com
Uuid: 9692eb2e-4655-4922-b0a3-cbbda3aa1a3e
State: Peer in Cluster (Connected)
Hostname: glusterfs-2.example.com
Uuid: 17dd8f27-c595-462b-b62c-71bbebce66ce
State: Peer in Cluster (Connected)
Set up GlusterFS Replicated Volume
Below is the syntax used to create glusterfs replicated volume
# gluster volume create NEW-VOLNAME [replica COUNT] [transport [tcp |rdma | tcp,rdma]] NEW-BRICK...
For example here I am creating a new glusterfs replicated volume "replicated_volume
" on all my cluster nodes i.e. glusterfs-1
, glusterfs-2
and glusterfs-3
.
It is going to replicate all the files over the three bricks under the new directory rep_vol
which will be created by the below command:
[root@glusterfs-1 ~]# gluster volume create replicated_volume replica 3 glusterfs-1:/bricks/brick1/rep_vol glusterfs-2:/bricks/brick2/rep_vol glusterfs-3:/bricks/brick3/rep_vol volume create: replicated_volume: success: please start the volume to access data
What is Split Brain?
Split brain is where at least two servers serving the same application in a cluster can no longer see each other and yet they still respond to clients. In this situation, data integrity and consistency start to drift apart as both servers continue to serve and store data but can no longer sync any data between each other.
Replica 2 volumes are prone to split-brain. Use Arbiter or Replica 3 to avoid this. See: http://docs.gluster.org/en/latest/Administrator%20Guide/Split%20brain%20and%20ways%20to%20deal%20with%20it/.
Next start the volume you created
[root@glusterfs-1 ~]# gluster volume start replicated_volume volume start: replicated_volume: success
To get more info on the replicated_volume
[root@glusterfs-1 ~]# gluster volume info replicated_volume
Volume Name: replicated_volume
Type: Replicate
Volume ID: a9740dad-0102-4131-8a08-74f3b2ec6103
Status: Started
Snapshot Count: 0
Number of Bricks: 1 x 3 = 3
Transport-type: tcp
Bricks:
Brick1: glusterfs-1:/bricks/brick1/rep_vol
Brick2: glusterfs-2:/bricks/brick2/rep_vol
Brick3: glusterfs-3:/bricks/brick3/rep_vol
Options Reconfigured:
features.shard: enable
performance.client-io-threads: off
nfs.disable: on
storage.fips-mode-rchecksum: on
transport.address-family: inet
/var/log/glusterfs/glusterd.log
should be checked in order to debug and diagnose the situation. These logs can be looked at on one or, all the servers configured.
Testing the GlusterFS Replicated Volume
For this step, we will use one of the servers to mount the volume. Typically, you would do this from an external machine, known as a "client
". Since using this method would require additional packages to be installed on the client machine, we will use one of the servers as a simple place to test first , as if it were that "client
".
On client gluster-fuse
rpm must be installed manually
# rpm -Uvh https://buildlogs.centos.org/centos/8/storage/x86_64/gluster-9/Packages/g/glusterfs-fuse-9.4-1.el8.x86_64.rpm
Since I am using one of the gluster nodes, the client package is already installed here
[root@glusterfs-1 ~]# rpm -q glusterfs-fuse glusterfs-fuse-9.4-1.el8.x86_64
Create a mount point
[root@glusterfs-1 ~]# mkdir /my_repvol
Mount the Gluster Replicated Volume as shown below:
[root@glusterfs-1 ~]# mount -t glusterfs glusterfs-1.example.com:/replicated_volume /my_repvol
[root@glusterfs-1 ~]# df -Th /my_repvol
Filesystem Type Size Used Avail Use% Mounted on
glusterfs-1.example.com:/replicated_volume fuse.glusterfs 2.0G 68M 2.0G 4% /my_repvol
Repeat the step on each gluster node
[root@glusterfs-2 ~]# mkdir /my_repvol
[root@glusterfs-2 ~]# mount -t glusterfs glusterfs-1.example.com:/replicated_volume /my_repvol
[root@glusterfs-2 ~]# df -Th /my_repvol
Filesystem Type Size Used Avail Use% Mounted on
glusterfs-1.example.com:/replicated_volume fuse.glusterfs 2.0G 68M 2.0G 4% /my_repvol
[root@glusterfs-3 ~]# mkdir /my_repvol
[root@glusterfs-3 ~]# mount -t glusterfs glusterfs-1.example.com:/replicated_volume /my_repvol
[root@glusterfs-3 ~]# df -Th /my_repvol
Filesystem Type Size Used Avail Use% Mounted on
glusterfs-1.example.com:/replicated_volume fuse.glusterfs 2.0G 68M 2.0G 4% /my_repvol
Next I will create 5 files on the replicated_volume
[root@glusterfs-1 ~]# touch /my_repvol/file{1..5}
Verify the list of files on the gluster nodes:
[root@glusterfs-1 ~]# ls -l /bricks/brick1/rep_vol/ total 0 -rw-r--r-- 2 root root 0 Jan 27 11:37 file1 -rw-r--r-- 2 root root 0 Jan 27 11:37 file2 -rw-r--r-- 2 root root 0 Jan 27 11:37 file3 -rw-r--r-- 2 root root 0 Jan 27 11:37 file4 -rw-r--r-- 2 root root 0 Jan 27 11:37 file5 [root@glusterfs-2 ~]# ls -l /bricks/brick2/rep_vol/ total 0 -rw-r--r-- 2 root root 0 Jan 27 11:37 file1 -rw-r--r-- 2 root root 0 Jan 27 11:37 file2 -rw-r--r-- 2 root root 0 Jan 27 11:37 file3 -rw-r--r-- 2 root root 0 Jan 27 11:37 file4 -rw-r--r-- 2 root root 0 Jan 27 11:37 file5 [root@glusterfs-3 ~]# ls -l /bricks/brick3/rep_vol/ total 0 -rw-r--r-- 2 root root 0 Jan 27 11:37 file1 -rw-r--r-- 2 root root 0 Jan 27 11:37 file2 -rw-r--r-- 2 root root 0 Jan 27 11:37 file3 -rw-r--r-- 2 root root 0 Jan 27 11:37 file4 -rw-r--r-- 2 root root 0 Jan 27 11:37 file5
So as expected the files are replicated across the gluster nodes.
Lastly I hope the steps from the article to install and configure glusterfs replicated volume on RHEL/CentOS 8 Linux was helpful. So, let me know your suggestions and feedback using the comment section.