High-Availability Storage With GlusterFS On Mandriva 2010.0 - Automatic File Replication Across Two Storage Servers - Page 2

3 Setting Up The GlusterFS Client

client1.example.com:

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

urpmi glusterfs-client glusterfs-server

Then we create the following directory:

mkdir /mnt/glusterfs

Next we create the file /etc/glusterfs/glusterfs.vol:

vi /etc/glusterfs/glusterfs.vol

volume remote1
  type protocol/client
  option transport-type tcp
  option remote-host server1.example.com
  option remote-subvolume brick
end-volume

volume remote2
  type protocol/client
  option transport-type tcp
  option remote-host server2.example.com
  option remote-subvolume brick
end-volume

volume replicate
  type cluster/replicate
  subvolumes remote1 remote2
end-volume

volume writebehind
  type performance/write-behind
  option window-size 1MB
  subvolumes replicate
end-volume

volume cache
  type performance/io-cache
  option cache-size 512MB
  subvolumes writebehind
end-volume

Make sure you use the correct server hostnames or IP addresses in the option remote-host lines!

That's it! Now we can mount the GlusterFS filesystem to /mnt/glusterfs with one of the following two commands:

glusterfs -f /etc/glusterfs/glusterfs.vol /mnt/glusterfs

or

mount -t glusterfs /etc/glusterfs/glusterfs.vol /mnt/glusterfs

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

mount

[root@client1 administrator]# mount
/dev/sda1 on / type ext4 (rw,relatime)
none on /proc type proc (rw)
/dev/sda6 on /home type ext4 (rw,relatime)
none on /proc/sys/fs/binfmt_misc type binfmt_misc (rw)
rpc_pipefs on /var/lib/nfs/rpc_pipefs type rpc_pipefs (rw)
nfsd on /proc/fs/nfsd type nfsd (rw)
/etc/glusterfs/glusterfs.vol on /mnt/glusterfs type fuse.glusterfs (rw,allow_other,default_permissions,max_read=131072)
[root@client1 administrator]#

... and...

df -h

[root@client1 administrator]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda1              12G  1.5G  9.8G  13% /
/dev/sda6              16G  172M   16G   2% /home
/etc/glusterfs/glusterfs.vol
                       29G  1.7G   26G   6% /mnt/glusterfs
[root@client1 administrator]#

(server1.example.com and server2.example.com each have 29GB of space for the GlusterFS filesystem, but because the data is mirrored, the client doesn't see 58GB (2 x 29GB), but only 29GB.)

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

[...]
/etc/glusterfs/glusterfs.vol  /mnt/glusterfs  glusterfs  defaults  0  0

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

Now let's check the /data/export 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/export

[root@server1 administrator]# ls -l /data/export
total 0
-rw-r--r-- 1 root root 0 2009-12-18 15:37 test1
-rw-r--r-- 1 root root 0 2009-12-18 15:37 test2
[root@server1 administrator]#

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/export directory on server2.example.com:

server2.example.com:

ls -l /data/export

[root@server2 administrator]# ls -l /data/export
total 0
-rw-r--r-- 1 root root 0 2009-12-18 15:37 test1
-rw-r--r-- 1 root root 0 2009-12-18 15:39 test3
-rw-r--r-- 1 root root 0 2009-12-18 15:39 test4
[root@server2 administrator]#

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

server1.example.com:

ls -l /data/export

[root@server1 administrator]# ls -l /data/export
total 0
-rw-r--r-- 1 root root 0 2009-12-18 15:37 test1
-rw-r--r-- 1 root root 0 2009-12-18 15:37 test2
[root@server1 administrator]#

As you see, server1.example.com hasn't noticed the changes that happened while it was 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 administrator]# ls -l /mnt/glusterfs/
total 0
-rw-r--r-- 1 root root 0 2009-12-18 15:37 test1
-rw-r--r-- 1 root root 0 2009-12-18 15:39 test3
-rw-r--r-- 1 root root 0 2009-12-18 15:39 test4
[root@client1 administrator]#

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

server1.example.com:

ls -l /data/export

[root@server1 administrator]# ls -l /data/export
total 0
-rw-r--r-- 1 root root 0 2009-12-18 15:37 test1
-rw-r--r-- 1 root root 0 2009-12-18 15:39 test3
-rw-r--r-- 1 root root 0 2009-12-18 15:39 test4
[root@server1 administrator]#

5 Links

• GlusterFS: http://www.gluster.org/
• Mandriva: http://www.mandriva.com/