Distributed Replicated Storage Across Four Storage Nodes With GlusterFS 3.2.x On Ubuntu 12.10 - Page 2

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 or server4.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, and server4.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 and server4) 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 2012-12-17 15:49 test1
-rw-r--r-- 1 root root 0 2012-12-17 15:49 test2
-rw-r--r-- 1 root root 0 2012-12-17 15:49 test4
-rw-r--r-- 1 root root 0 2012-12-17 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 2012-12-17 15:49 test1
-rw-r--r-- 1 root root 0 2012-12-17 15:49 test2
-rw-r--r-- 1 root root 0 2012-12-17 15:49 test4
-rw-r--r-- 1 root root 0 2012-12-17 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 2012-12-17 15:49 test3
-rw-r--r-- 1 root root 0 2012-12-17 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 2012-12-17 15:49 test3
-rw-r--r-- 1 root root 0 2012-12-17 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 on client1.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 and server3.example.com:

server2.example.com:

ls -l /data

root@server2:~# ls -l /data
total 0
-rw-r--r-- 1 root root 0 2012-12-17 15:49 test1
-rw-r--r-- 1 root root 0 2012-12-17 15:49 test2
-rw-r--r-- 1 root root 0 2012-12-17 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 2012-12-17 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 2012-12-17 15:49 test1
-rw-r--r-- 1 root root 0 2012-12-17 15:49 test2
-rw-r--r-- 1 root root 0 2012-12-17 15:49 test4
-rw-r--r-- 1 root root 0 2012-12-17 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 2012-12-17 15:49 test3
-rw-r--r-- 1 root root 0 2012-12-17 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 2012-12-17 15:49 test1
-rw-r--r-- 1 root root 0 2012-12-17 15:49 test2
-rw-r--r-- 1 root root 0 2012-12-17 15:49 test3
-rw-r--r-- 1 root root 0 2012-12-17 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 2012-12-17 15:49 test1
-rw-r--r-- 1 root root 0 2012-12-17 15:49 test2
-rw-r--r-- 1 root root 0 2012-12-17 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 2012-12-17 15:49 test3
root@server4:~#

 

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