Distributed Replicated Storage Across Four Storage Nodes With GlusterFS 3.2.x On Ubuntu 12.04

This tutorial shows how to combine four single storage servers (running Ubuntu 12.04) to a distributed replicated storage withGlusterFS. Nodes 1 and 2 (replication1) as well as 3 and 4 (replication2) will mirror each other, and replication1 and replication2 will be combined to one larger storage server (distribution). Basically, this is RAID10 over network. If you lose one server from replication1 and one from replication2, the distributed volume continues to work. The client system (Ubuntu 12.04 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 use five systems, four servers and a client:

• server1.example.com: IP address 192.168.0.100 (server)
• server2.example.com: IP address 192.168.0.101 (server)
• server3.example.com: IP address 192.168.0.102 (server)
• server4.example.com: IP address 192.168.0.103 (server)
• client1.example.com: IP address 192.168.0.104 (client)

Because we will run all the steps from this tutorial with root privileges, we can either prepend all commands in this tutorial with the stringsudo, or we become root right now by typing

sudo su

All five 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 five systems:

vi /etc/hosts

127.0.0.1 localhost.localdomain localhost 192.168.0.100 server1.example.com server1 192.168.0.101 server2.example.com server2 192.168.0.102 server3.example.com server3 192.168.0.103 server4.example.com server4 192.168.0.104 client1.example.com client1 # The following lines are desirable for IPv6 capable hosts ::1 localhost ip6-localhost ip6-loopback fe00::0 ip6-localnet ff00::0 ip6-mcastprefix ff02::1 ip6-allnodes ff02::2 ip6-allrouters ff02::3 ip6-allhosts

(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/server3.example.com/server4.example.com:

GlusterFS is available as a package for Ubuntu 12.04, therefore we can install it as follows:

apt-get install glusterfs-server

The command

glusterfsd --version

should now show the GlusterFS version that you've just installed (3.2.5 in this case):

root@server1:~# glusterfsd --version
glusterfs 3.2.5 built on Jan 31 2012 07:39:58
Repository revision: git://git.gluster.com/glusterfs.git
Copyright (c) 2006-2011 Gluster Inc. <http://www.gluster.com>
GlusterFS comes with ABSOLUTELY NO WARRANTY.
You may redistribute copies of GlusterFS under the terms of the GNU General Public License.
root@server1:~#

If you use a firewall, ensure that TCP ports 111, 24007, 24008, 24009-(24009 + number of bricks across all volumes) are open onserver1.example.com, server2.example.com, server3.example.com, and server4.example.com.

Next we must add server2.example.com, server3.example.com, and server4.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 fromserver2.example.com or server3.example.com or server4.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
gluster peer probe server3.example.com
gluster peer probe server4.example.com

Output should be as follows:

root@server1:~# gluster peer probe server2.example.com
Probe successful
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: 3

Hostname: server2.example.com
Uuid: 600ff607-f7fd-43f6-af8d-419df703376d
State: Peer in Cluster (Connected)

Hostname: server3.example.com
Uuid: 1d6a5f3f-c2dd-4727-a050-0431772cc381
State: Peer in Cluster (Connected)

Hostname: server4.example.com
Uuid: 0bd9d445-0b5b-4a91-be6f-02b13c41d5d6
State: Peer in Cluster (Connected)
root@server1:~#

Next we create the distributed replicated share named testvol with two replicas (please note that the number of replicas is half the number of servers in this case because we want to set up distributed replication) on server1.example.com, server2.example.com,server3.example.com, and server4.example.com in the /data directory (this will be created if it doesn't exist):

gluster volume create testvol replica 2 transport tcp server1.example.com:/data server2.example.com:/data server3.example.com:/data server4.example.com:/data

root@server1:~# gluster volume create testvol replica 2 transport tcp server1.example.com:/data server2.example.com:/data server3.example.com:/data server4.example.com:/data
Creation of volume testvol has been successful. Please start the volume to access data.
root@server1:~#

Start the volume:

gluster volume start testvol

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/server3.example.com/server4.example.com:

netstat -tap | grep glusterfsd

on both servers.

If you get output like this...

root@server1:~# netstat -tap | grep glusterfsd
tcp        0      0 *:24009                 *:*                     LISTEN      1110/glusterfsd
tcp        0      0 localhost.localdom:1019 localhost.localdo:24007 ESTABLISHED 1110/glusterfsd
root@server1:~#

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

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

root@server3:~# netstat -tap | grep glusterfsd
root@server3:~#

root@server4:~# netstat -tap | grep glusterfsd
root@server4:~#

... restart the GlusterFS daemon on the corresponding server (server2.example.com, server3.example.com, and server4.example.com in this case):

server2.example.com/server3.example.com/server4.example.com:

/etc/init.d/glusterfs-server restart

Then check the output of...

netstat -tap | grep glusterfsd

... again on these servers - it should now look like this:

root@server2:~# netstat -tap | grep glusterfsd
tcp        0      0 *:24009                 *:*                     LISTEN      1152/glusterfsd
tcp        0      0 localhost.localdom:1018 localhost.localdo:24007 ESTABLISHED 1152/glusterfsd
root@server2:~#

root@server3:~# netstat -tap | grep glusterfsd
tcp        0      0 *:24009                 *:*                     LISTEN      1311/glusterfsd
tcp        0      0 localhost.localdom:1018 localhost.localdo:24007 ESTABLISHED 1311/glusterfsd
root@server3:~#

root@server4:~# netstat -tap | grep glusterfsd
tcp        0      0 *:24009                 *:*                     LISTEN      1297/glusterfsd
tcp        0      0 localhost.localdom:1019 localhost.localdo:24007 ESTABLISHED 1297/glusterfsd
root@server4:~#

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: Distributed-Replicate
Status: Started
Number of Bricks: 2 x 2 = 4
Transport-type: tcp
Bricks:
Brick1: server1.example.com:/data
Brick2: server2.example.com:/data
Brick3: server3.example.com:/data
Brick4: server4.example.com:/data
root@server1:~#

By default, all clients can connect to the volume. If you want to grant access to client1.example.com (= 192.168.0.104) only, run:

gluster volume set testvol auth.allow 192.168.0.104

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. 192.168.0.104,192.168.0.105).

The volume info should now show the updated status:

gluster volume info

root@server1:~# gluster volume info

Volume Name: testvol
Type: Distributed-Replicate
Status: Started
Number of Bricks: 2 x 2 = 4
Transport-type: tcp
Bricks:
Brick1: server1.example.com:/data
Brick2: server2.example.com:/data
Brick3: server3.example.com:/data
Brick4: server4.example.com:/data
Options Reconfigured:
auth.allow: 192.168.0.104
root@server1:~#

3 Setting Up The GlusterFS Client

client1.example.com:

On the client, we can install the GlusterFS client as follows:

apt-get 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 or server3.example.com or server4.example.com in the above command!)

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

mount

root@client1:~# mount
/dev/mapper/server5-root on / type ext4 (rw,errors=remount-ro)
proc on /proc type proc (rw,noexec,nosuid,nodev)
sysfs on /sys type sysfs (rw,noexec,nosuid,nodev)
fusectl on /sys/fs/fuse/connections type fusectl (rw)
none on /sys/kernel/debug type debugfs (rw)
none on /sys/kernel/security type securityfs (rw)
udev on /dev type devtmpfs (rw,mode=0755)
devpts on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=0620)
tmpfs on /run type tmpfs (rw,noexec,nosuid,size=10%,mode=0755)
none on /run/lock type tmpfs (rw,noexec,nosuid,nodev,size=5242880)
none on /run/shm type tmpfs (rw,nosuid,nodev)
/dev/sda1 on /boot type ext2 (rw)
server1.example.com:/testvol on /mnt/glusterfs type fuse.glusterfs (rw,allow_other,default_permissions,max_read=131072)
root@client1:~#

... and...

df -h

root@client1:~# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/server5-root
                       29G  1.1G   27G   4% /
udev                  238M  4.0K  238M   1% /dev
tmpfs                  99M  212K   99M   1% /run
none                  5.0M     0  5.0M   0% /run/lock
none                  247M     0  247M   0% /run/shm
/dev/sda1             228M   24M  193M  11% /boot
server1.example.com:/testvol
                       58G  2.1G   53G   4% /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:

vi /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 or server3.example.com orserver4.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

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

client1.example.com:

touch /mnt/glusterfs/test1
touch /mnt/glusterfs/test2
touch /mnt/glusterfs/test3
touch /mnt/glusterfs/test4
touch /mnt/glusterfs/test5
touch /mnt/glusterfs/test6

Now let's check the /data directory on server1.example.com, server2.example.com, server3.example.com, andserver4.example.com. You will notice that replication1 as well as replication2 hold only a part of the files/directories that make up the GlusterFS share on the client, but the nodes that make up replication1 (server1 and server2) or replication2 (server3 andserver4) contain the same files (mirroring):

server1.example.com:

ls -l /data

root@server1:~# ls -l /data
total 0
-rw-r--r-- 1 root root 0 2012-05-29 15:49 test1
-rw-r--r-- 1 root root 0 2012-05-29 15:49 test2
-rw-r--r-- 1 root root 0 2012-05-29 15:49 test4
-rw-r--r-- 1 root root 0 2012-05-29 15:49 test5
root@server1:~#

server2.example.com:

ls -l /data

root@server2:~# ls -l /data
total 0
-rw-r--r-- 1 root root 0 2012-05-29 15:49 test1
-rw-r--r-- 1 root root 0 2012-05-29 15:49 test2
-rw-r--r-- 1 root root 0 2012-05-29 15:49 test4
-rw-r--r-- 1 root root 0 2012-05-29 15:49 test5
root@server2:~#

server3.example.com:

ls -l /data

root@server3:~# ls -l /data
total 0
-rw-r--r-- 1 root root 0 2012-05-29 15:49 test3
-rw-r--r-- 1 root root 0 2012-05-29 15:49 test6
root@server3:~#

server4.example.com:

ls -l /data

root@server4:~# ls -l /data
total 0
-rw-r--r-- 1 root root 0 2012-05-29 15:49 test3
-rw-r--r-- 1 root root 0 2012-05-29 15:49 test6
root@server4:~#

Now we shut down server1.example.com and server4.example.com and add/delete some files on the GlusterFS share onclient1.example.com.

server1.example.com/server4.example.com:

shutdown -h now

client1.example.com:

rm -f /mnt/glusterfs/test5
rm -f /mnt/glusterfs/test6

The changes should be visible in the /data directory on server2.example.com andserver3.example.com:

server2.example.com:

ls -l /data

root@server2:~# ls -l /data
total 0
-rw-r--r-- 1 root root 0 2012-05-29 15:49 test1
-rw-r--r-- 1 root root 0 2012-05-29 15:49 test2
-rw-r--r-- 1 root root 0 2012-05-29 15:49 test4
root@server2:~#

server3.example.com:

ls -l /data

root@server3:~# ls -l /data
total 0
-rw-r--r-- 1 root root 0 2012-05-29 15:49 test3
root@server3:~#

Let's boot server1.example.com and server4.example.com again and take a look at the /data directory:

server1.example.com:

ls -l /data

root@server1:~# ls -l /data
total 0
-rw-r--r-- 1 root root 0 2012-05-29 15:49 test1
-rw-r--r-- 1 root root 0 2012-05-29 15:49 test2
-rw-r--r-- 1 root root 0 2012-05-29 15:49 test4
-rw-r--r-- 1 root root 0 2012-05-29 15:49 test5
root@server1:~#

server4.example.com:

ls -l /data

root@server4:~# ls -l /data
total 0
-rw-r--r-- 1 root root 0 2012-05-29 15:49 test3
-rw-r--r-- 1 root root 0 2012-05-29 15:49 test6
root@server4:~#

As you see, server1.example.com and server4.example.com haven't noticed the changes that happened while they were down. 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 2012-05-29 15:49 test1
-rw-r--r-- 1 root root 0 2012-05-29 15:49 test2
-rw-r--r-- 1 root root 0 2012-05-29 15:49 test3
-rw-r--r-- 1 root root 0 2012-05-29 15:49 test4
root@client1:~#

Now take a look at the /data directory on server1.example.com and server4.example.com again, and you should see that the changes have been replicated to these nodes:

server1.example.com:

ls -l /data

root@server1:~# ls -l /data
total 0
-rw-r--r-- 1 root root 0 2012-05-29 15:49 test1
-rw-r--r-- 1 root root 0 2012-05-29 15:49 test2
-rw-r--r-- 1 root root 0 2012-05-29 15:49 test4
root@server1:~#

server4.example.com:

ls -l /data

root@server4:~# ls -l /data
total 0
-rw-r--r-- 1 root root 0 2012-05-29 15:49 test3
root@server4:~#

Version 1.0 
Author: Falko Timme 

source : howtoforge

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