There is a new version of this tutorial available for Debian 12 (Bookworm).

High-Availability Storage with GlusterFS on Debian 8 - Mirror across two storage servers

This tutorial shows how to set up a high-availability storage with two storage servers (Debian Jessie) that uses GlusterFS. Each storage server will be a mirror of the other storage server, and files will be replicated automatically across both storage nodes. The client system (Debian 8 as well) will be able to access the storage as if it was a local filesystem. GlusterFS is a clustered file-system capable of scaling to several peta-bytes. It aggregates various storage bricks over Infiniband RDMA or TCP/IP interconnect into one large parallel network file system. Storage bricks can be made of any commodity hardware such as x86_64 servers with SATA-II RAID and Infiniband HBA.

 

1 Preliminary Note

In this tutorial, I will use three systems, two servers and a client:

  • server1.example.com: IP address 192.168.1.100 (server)
  • server2.example.com: IP address 192.168.1.101 (server)
  • client1.example.com: IP address 192.168.1.102 (client)

All three systems should be able to resolve the other systems' hostnames. If this cannot be done through DNS, you should edit the /etc/hosts file so that it looks as follows on all three systems:

nano /etc/hosts
127.0.0.1 localhost
192.168.1.100 server1.example.com server1
192.168.1.101 server2.example.com server2
192.168.1.102 client1.example.com client1


# The following lines are desirable for IPv6 capable hosts
::1 localhost ip6-localhost ip6-loopback
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters

(It is also possible to use IP addresses instead of hostnames in the following setup. If you prefer to use IP addresses, you don't have to care about whether the hostnames can be resolved or not.)

 

2 Setting up the GlusterFS Servers

server1.example.com/server2.example.com:

The latest GlusterFS version is available as Debian package from gluster.org. We can install it as follows:

We add the public key of the gluster.org Debian repository on both servers.

wget -O - http://download.gluster.org/pub/gluster/glusterfs/3.7/3.7.9/rsa.pub | apt-key add -

Then add the GlusterFS repository (the command is one line!)

echo deb http://download.gluster.org/pub/gluster/glusterfs/3.7/3.7.9/Debian/jessie/apt jessie main > /etc/apt/sources.list.d/gluster.list

and update the repository list.

apt-get update

Now we can install the GlusterFS server software with apt.

apt-get -y install glusterfs-server

The command

glusterfsd --version

should now show the GlusterFS version that you've just installed (3.7.9 in this case):

root@server1:/# glusterfsd --version
glusterfs 3.7.9 built on Mar 23 2016 05:24:49
Repository revision: git://git.gluster.com/glusterfs.git
Copyright (c) 2006-2013 Red Hat, Inc. <http://www.redhat.com/>
GlusterFS comes with ABSOLUTELY NO WARRANTY.
It is licensed to you under your choice of the GNU Lesser
General Public License, version 3 or any later version (LGPLv3
or later), or the GNU General Public License, version 2 (GPLv2),
in all cases as published by the Free Software Foundation.
root@server1:/#

If you use a firewall, ensure that TCP ports 111, 24007, 24008, 24009-(24009 + number of bricks across all volumes) are open on server1.example.com and server2.example.com.

Glusterfs shall store its data in the directory /data on the servers. This location can be a normal directory if you have a smaller installation or you use a separate hard disk partition and mount it as /data.

Run on both servers:

mkdir /data

to create the data directory.

Next, we must add server2.example.com to the trusted storage pool (please note that I'm running all GlusterFS configuration commands from server1.example.com, but you can as well run them from server2.example.com because the configuration is repliacted between the GlusterFS nodes - just make sure you use the correct hostnames or IP addresses):

server1.example.com:

On server1.example.com, run

gluster peer probe server2.example.com
root@server1:/# gluster peer probe server2.example.com
peer probe: success.
root@server1:/#

The status of the trusted storage pool should now be similar to this:

gluster peer status
root@server1:/# gluster peer status
Number of Peers: 1
Hostname: server2.example.com
Uuid: 0f7ee46c-6a71-4a31-91d9-6076707eff95
State: Peer in Cluster (Connected)
root@server1:/#

Next we create the share named testvol with two replicas (please note that the number of replicas is equal to the number of servers in this case because we want to set up mirroring) on server1.example.com and server2.example.com in the /data/testvol directory (this will be created if it doesn't exist):

gluster volume create testvol replica 2 transport tcp server1.example.com:/data/testvol server2.example.com:/data/testvol force
root@server1:/# gluster volume create testvol replica 2 transport tcp server1.example.com:/data/testvol server2.example.com:/data/testvol force
volume create: testvol: success: please start the volume to access data
root@server1:/#

Start the volume:

gluster volume start testvol
root@server1:/# gluster volume start testvol
volume start: testvol: success
root@server1:/#

Our test volume has been started successfully.

It is possible that the above command tells you that the action was not successful:

root@server1:~# gluster volume start testvol
Starting volume testvol has been unsuccessful
root@server1:~#

In this case you should check the output of...

server1.example.com/server2.example.com:

netstat -tap | grep glusterfsd

on both servers.

If you get output like this...

root@server1:/# netstat -tap | grep glusterfsd
tcp 0 0 *:49152 *:* LISTEN 8007/glusterfsd
tcp 0 0 server1.example.c:65533 server1.example.c:24007 ESTABLISHED 8007/glusterfsd
tcp 0 0 server1.example.c:49152 server2.example.c:65531 ESTABLISHED 8007/glusterfsd
tcp 0 0 server1.example.c:49152 server1.example.c:65532 ESTABLISHED 8007/glusterfsd
tcp 0 0 server1.example.c:49152 server1.example.c:65531 ESTABLISHED 8007/glusterfsd
tcp 0 0 server1.example.c:49152 server2.example.c:65526 ESTABLISHED 8007/glusterfsd
root@server1:/#

... everything is fine, but if you don't get any output...

root@server2:~# netstat -tap | grep glusterfsd
root@server2:~#

... restart the GlusterFS daemon on the corresponding server (server1.example.com in this case):

server2.example.com:

service glusterfs-server restart

Then check the output of...

netstat -tap | grep glusterfsd

... again on that server - it should now look like this:

root@server2:/# netstat -tap | grep glusterfsd
tcp 0 0 *:49152 *:* LISTEN 7852/glusterfsd
tcp 0 0 server2.example.c:49152 server2.example.c:65532 ESTABLISHED 7852/glusterfsd
tcp 0 0 server2.example.c:49152 server1.example.c:65526 ESTABLISHED 7852/glusterfsd
tcp 0 0 server2.example.c:49152 server2.example.c:65525 ESTABLISHED 7852/glusterfsd
tcp 0 0 server2.example.c:65533 server2.example.c:24007 ESTABLISHED 7852/glusterfsd
tcp 0 0 server2.example.c:49152 server1.example.c:65524 ESTABLISHED 7852/glusterfsd
root@server2:/#

Now back to server1.example.com:

server1.example.com:

You can check the status of the volume with the command

gluster volume info
root@server1:/# gluster volume info
Volume Name: testvol
Type: Replicate
Volume ID: 3fc9af57-ca56-4a72-ad54-3d2ea03e5883
Status: Started
Number of Bricks: 1 x 2 = 2
Transport-type: tcp
Bricks:
Brick1: server1.example.com:/data/testvol
Brick2: server2.example.com:/data/testvol
Options Reconfigured:
performance.readdir-ahead: on
root@server1:/#

By default, all clients can connect to the volume. If you want to grant access to client1.example.com (= 192.168.1.102) only, run:

gluster volume set testvol auth.allow 192.168.1.102
root@server1:/# gluster volume set testvol auth.allow 192.168.1.102
volume set: success
root@server1:/#

Please note that it is possible to use wildcards for the IP addresses (like 192.168.*) and that you can specify multiple IP addresses separated by comma (e.g. 192.168.1.102,192.168.1.103).

The volume info should now show the updated status:

gluster volume info

root@server1:/# gluster volume info

Volume Name: testvol
Type: Replicate
Volume ID: 3fc9af57-ca56-4a72-ad54-3d2ea03e5883
Status: Started
Number of Bricks: 1 x 2 = 2
Transport-type: tcp
Bricks:
Brick1: server1.example.com:/data/testvol
Brick2: server2.example.com:/data/testvol
Options Reconfigured:
auth.allow: 192.168.1.102
performance.readdir-ahead: on
root@server1:/#

 

3 Setting up the GlusterFS Client

client1.example.com:

On the client system we add the public key of the gluster.org Debian repository first.

wget -O - http://download.gluster.org/pub/gluster/glusterfs/3.7/3.7.9/rsa.pub | apt-key add -

Then add the GlusterFS repository (the command is one line!)

echo deb http://download.gluster.org/pub/gluster/glusterfs/3.7/3.7.9/Debian/jessie/apt jessie main > /etc/apt/sources.list.d/gluster.list

and update the repository list.

apt-get update

Now we can install the GlusterFS client as follows.

apt-get -y install glusterfs-client

Then we create the following directory:

mkdir /mnt/glusterfs

That's it! Now we can mount the GlusterFS filesystem to /mnt/glusterfs with the following command:

mount.glusterfs server1.example.com:/testvol /mnt/glusterfs

(Instead of server1.example.com you can as well use server2.example.com in the above command!)

You should now see the new share in the outputs of...

mount
root@client1:/# mount
sysfs on /sys type sysfs (rw,nosuid,nodev,noexec,relatime)
proc on /proc type proc (rw,nosuid,nodev,noexec,relatime)
udev on /dev type devtmpfs (rw,relatime,size=10240k,nr_inodes=125556,mode=755)
devpts on /dev/pts type devpts (rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000)
tmpfs on /run type tmpfs (rw,nosuid,relatime,size=204220k,mode=755)
/dev/sda1 on / type ext4 (rw,relatime,errors=remount-ro,data=ordered)
securityfs on /sys/kernel/security type securityfs (rw,nosuid,nodev,noexec,relatime)
tmpfs on /dev/shm type tmpfs (rw,nosuid,nodev)
tmpfs on /run/lock type tmpfs (rw,nosuid,nodev,noexec,relatime,size=5120k)
tmpfs on /sys/fs/cgroup type tmpfs (ro,nosuid,nodev,noexec,mode=755)
cgroup on /sys/fs/cgroup/systemd type cgroup (rw,nosuid,nodev,noexec,relatime,xattr,release_agent=/lib/systemd/systemd-cgroups-agent,name=systemd)
pstore on /sys/fs/pstore type pstore (rw,nosuid,nodev,noexec,relatime)
cgroup on /sys/fs/cgroup/cpuset type cgroup (rw,nosuid,nodev,noexec,relatime,cpuset)
cgroup on /sys/fs/cgroup/cpu,cpuacct type cgroup (rw,nosuid,nodev,noexec,relatime,cpu,cpuacct)
cgroup on /sys/fs/cgroup/devices type cgroup (rw,nosuid,nodev,noexec,relatime,devices)
cgroup on /sys/fs/cgroup/freezer type cgroup (rw,nosuid,nodev,noexec,relatime,freezer)
cgroup on /sys/fs/cgroup/net_cls,net_prio type cgroup (rw,nosuid,nodev,noexec,relatime,net_cls,net_prio)
cgroup on /sys/fs/cgroup/blkio type cgroup (rw,nosuid,nodev,noexec,relatime,blkio)
cgroup on /sys/fs/cgroup/perf_event type cgroup (rw,nosuid,nodev,noexec,relatime,perf_event)
systemd-1 on /proc/sys/fs/binfmt_misc type autofs (rw,relatime,fd=23,pgrp=1,timeout=300,minproto=5,maxproto=5,direct)
mqueue on /dev/mqueue type mqueue (rw,relatime)
debugfs on /sys/kernel/debug type debugfs (rw,relatime)
hugetlbfs on /dev/hugepages type hugetlbfs (rw,relatime)
rpc_pipefs on /run/rpc_pipefs type rpc_pipefs (rw,relatime)
fusectl on /sys/fs/fuse/connections type fusectl (rw,relatime)
server1.example.com:/testvol on /mnt/glusterfs type fuse.glusterfs (rw,relatime,user_id=0,group_id=0,default_permissions,allow_other,max_read=131072)
root@client1:/#

... and...

df -h
root@client1:/# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda1 57G 1.1G 53G 2% /
udev 10M 0 10M 0% /dev
tmpfs 200M 4.6M 195M 3% /run
tmpfs 499M 0 499M 0% /dev/shm
tmpfs 5.0M 0 5.0M 0% /run/lock
tmpfs 499M 0 499M 0% /sys/fs/cgroup
server1.example.com:/testvol 57G 21G 34G 39% /mnt/glusterfs
root@client1:/#

Instead of mounting the GlusterFS share manually on the client, you could modify /etc/fstab so that the share gets mounted automatically when the client boots.

Open /etc/fstab and append the following line:

nano /etc/fstab
[...]
server1.example.com:/testvol /mnt/glusterfs glusterfs defaults,_netdev 0 0

(Again, instead of server1.example.com you can as well use server2.example.com!)

To test if your modified /etc/fstab is working, reboot the client:

reboot

After the reboot, you should find the share in the outputs of...

df -h

... and...

mount

 

4 Testing GlusterFS Replication

Now let's create some test files on the GlusterFS share:

client1.example.com:

touch /mnt/glusterfs/test1
touch /mnt/glusterfs/test2

Now let's check the /data directory on server1.example.com and server2.example.com. The test1 and test2 files should be present on each node:

server1.example.com/server2.example.com:

ls -l /data/testvol
root@server1:/# ls -l /data/testvol/
total 0
-rw-r--r-- 2 root root 0 Mar 23 2016 test1
-rw-r--r-- 2 root root 0 Mar 23 2016 test2

Now we shut down server1.example.com and add/delete some files on the GlusterFS share on client1.example.com.

server1.example.com:

shutdown -h now

client1.example.com:

touch /mnt/glusterfs/test3
touch /mnt/glusterfs/test4
rm -f /mnt/glusterfs/test2

The changes should be visible in the /data/testvol directory on server2.example.com:

server2.example.com:

ls -l /data/testvol
root@server2:/# ls -l /data/testvol
total 8
-rw-r--r-- 2 root root 0 Mar 23 08:06 test1
-rw-r--r-- 2 root root 0 Mar 23 08:09 test3
-rw-r--r-- 2 root root 0 Mar 23 08:09 test4
root@server2:/#

Let's boot server1.example.com again and take a look at the /data directory:

server1.example.com:

ls -l /data/testvol
root@server1:/# ls -l /data/testvol
total 0
-rw-r--r-- 2 root root 0 Mar 23 08:06 test1
-rw-r--r-- 2 root root 0 Mar 23 08:09 test3
-rw-r--r-- 2 root root 0 Mar 23 08:09 test4
root@server1:/#

As you see, server1.example.com automatically synced the changed. In case that the change has not been synced yet, then this is easy to fix, all we need to do is invoke a read command on the GlusterFS share on client1.example.com, e.g.:

client1.example.com:

ls -l /mnt/glusterfs/
root@client1:/# ls -l /mnt/glusterfs/
total 0
-rw-r--r-- 1 root root 0 Mar 23 08:06 test1
-rw-r--r-- 1 root root 0 Mar 23 08:09 test3
-rw-r--r-- 1 root root 0 Mar 23 08:09 test4
root@client1:/#

 

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