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Distributed Replicated Storage Across Four Storage Nodes With GlusterFS On Mandriva 2010.0


This tutorial shows how to combine four single storage servers (running Mandriva 2010.0) to a distributed replicated storage with GlusterFS. 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 (Mandriva 2010.0 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.

I do not issue any guarantee that this will work for you!

 

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)

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

(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 Mandriva 2010.0, therefore we can install it as follows:

urpmi glusterfs-server

The command

glusterfs –version

should now show the GlusterFS version that you’ve just installed (2.0.6 in this case):

[root@server1 administrator]# glusterfs –version
glusterfs 2.0.6 built on Sep 20 2009 06:40:50
Repository revision: v2.0.6
Copyright (c) 2006-2009 Z RESEARCH Inc. <http://www.zresearch.com>
GlusterFS comes with ABSOLUTELY NO WARRANTY.
You may redistribute copies of GlusterFS under the terms of the GNU General Public License.
[root@server1 administrator]#

Next we create a few directories:

mkdir /data/
mkdir /data/export
mkdir /data/export-ns

Now we create the GlusterFS server configuration file /etc/glusterfs/glusterfsd.vol which defines which directory will be exported (/data/export) and what client is allowed to connect (192.168.0.104 = client1.example.com):

vi /etc/glusterfs/glusterfsd.vol

volume posix
  type storage/posix
  option directory /data/export
end-volume

volume locks
  type features/locks
  subvolumes posix
end-volume

volume brick
  type performance/io-threads
  option thread-count 8
  subvolumes locks
end-volume

volume server
  type protocol/server
  option transport-type tcp
  option auth.addr.brick.allow 192.168.0.104
  subvolumes brick
end-volume

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).

Afterwards we start the GlusterFS server:

/etc/init.d/glusterfsd restart

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 remote3
  type protocol/client
  option transport-type tcp
  option remote-host server3.example.com
  option remote-subvolume brick
end-volume

volume remote4
  type protocol/client
  option transport-type tcp
  option remote-host server4.example.com
  option remote-subvolume brick
end-volume

volume replicate1
  type cluster/replicate
  subvolumes remote1 remote2
end-volume

volume replicate2
  type cluster/replicate
  subvolumes remote3 remote4
end-volume

volume distribute
  type cluster/distribute
  subvolumes replicate1 replicate2
end-volume

volume writebehind
  type performance/write-behind
  option window-size 1MB
  subvolumes distribute
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
58G  1.7G   56G   3% /mnt/glusterfs
[root@client1 administrator]#

(The size of the distributed storage is calculated by replication1 + replication2, where both replication volumes are as big as the smallest brick.)

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

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

[root@server1 administrator]# ls -l /data/export
total 0
-rw-r–r– 1 root root 0 2009-12-21 15:41 test1
-rw-r–r– 1 root root 0 2009-12-21 15:41 test2
-rw-r–r– 1 root root 0 2009-12-21 15:41 test4
-rw-r–r– 1 root root 0 2009-12-21 15:41 test5
[root@server1 administrator]#

server2.example.com:

ls -l /data/export

[root@server2 administrator]# ls -l /data/export
total 0
-rw-r–r– 1 root root 0 2009-12-21 15:41 test1
-rw-r–r– 1 root root 0 2009-12-21 15:41 test2
-rw-r–r– 1 root root 0 2009-12-21 15:41 test4
-rw-r–r– 1 root root 0 2009-12-21 15:41 test5
[root@server2 administrator]#

server3.example.com:

ls -l /data/export

[root@server3 administrator]# ls -l /data/export
total 0
-rw-r–r– 1 root root 0 2009-12-21 15:41 test3
-rw-r–r– 1 root root 0 2009-12-21 15:41 test6
[root@server3 administrator]#

server4.example.com:

ls -l /data/export

[root@server4 administrator]# ls -l /data/export
total 0
-rw-r–r– 1 root root 0 2009-12-21 15:41 test3
-rw-r–r– 1 root root 0 2009-12-21 15:41 test6
[root@server4 administrator]#

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/export directory on server2.example.com and server3.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 2009-12-21 15:41 test1
-rw-r–r– 1 root root 0 2009-12-21 15:41 test2
-rw-r–r– 1 root root 0 2009-12-21 15:41 test4
[root@server2 administrator]#

server3.example.com:

ls -l /data/export

[root@server3 administrator]# ls -l /data/export
total 0
-rw-r–r– 1 root root 0 2009-12-21 15:41 test3
[root@server3 administrator]#

Let’s boot server1.example.com and server4.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 2009-12-21 15:41 test1
-rw-r–r– 1 root root 0 2009-12-21 15:41 test2
-rw-r–r– 1 root root 0 2009-12-21 15:41 test4
-rw-r–r– 1 root root 0 2009-12-21 15:41 test5
[root@server1 administrator]#

server4.example.com:

ls -l /data/export

[root@server4 administrator]# ls -l /data/export
total 0
-rw-r–r– 1 root root 0 2009-12-21 15:41 test3
-rw-r–r– 1 root root 0 2009-12-21 15:41 test6
[root@server4 administrator]#

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 administrator]# ls -l /mnt/glusterfs/
total 0
-rw-r–r– 1 root root 0 2009-12-21 15:41 test1
-rw-r–r– 1 root root 0 2009-12-21 15:41 test2
-rw-r–r– 1 root root 0 2009-12-21 15:41 test3
-rw-r–r– 1 root root 0 2009-12-21 15:41 test4
[root@client1 administrator]#

Now take a look at the /data/export 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/export

[root@server1 administrator]# ls -l /data/export
total 0
-rw-r–r– 1 root root 0 2009-12-21 15:41 test1
-rw-r–r– 1 root root 0 2009-12-21 15:41 test2
-rw-r–r– 1 root root 0 2009-12-21 15:41 test4
[root@server1 administrator]#

server4.example.com:

ls -l /data/export

[root@server4 administrator]# ls -l /data/export
total 0
-rw-r–r– 1 root root 0 2009-12-21 15:41 test3
[root@server4 administrator]#

 

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

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