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High-Availability Storage With GlusterFS On Debian Lenny – Automatic File Replication Across Two Storage Servers


This tutorial shows how to set up a high-availability storage with two storage servers (Debian Lenny) that use GlusterFS. Each storage server will be a mirror of the other storage server, and files will be replicated automatically across both storage servers. The client system (Debian Lenny 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 three systems, two servers and a client:

  • server1.example.com: IP address 192.168.0.100 (server)
  • server2.example.com: IP address 192.168.0.101 (server)
  • client1.example.com: IP address 192.168.0.102 (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:

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   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:

GlusterFS isn’t available as a Debian package for Debian Lenny, therefore we have to build it ourselves. First we install the prerequisites:

aptitude install sshfs build-essential flex bison byacc libdb4.6 libdb4.6-dev

Then we download the latest GlusterFS release from http://www.gluster.org/download.php and build it as follows:

cd /tmp
wget http://ftp.gluster.com/pub/gluster/glusterfs/2.0/LATEST/glusterfs-2.0.1.tar.gz
tar xvfz glusterfs-2.0.1.tar.gz
cd glusterfs-2.0.1
./configure –prefix=/usr > /dev/null

server1:/tmp/glusterfs-2.0.1# ./configure –prefix=/usr > /dev/null

GlusterFS configure summary
===========================
FUSE client        : no
Infiniband verbs   : no
epoll IO multiplex : yes
Berkeley-DB        : yes
libglusterfsclient : yes
mod_glusterfs      : no ()
argp-standalone    : no

server1:/tmp/glusterfs-2.0.1#

make && make install
ldconfig

The command

glusterfs –version

should now show the GlusterFS version that you’ve just compiled (2.0.1 in this case):

server1:/tmp/glusterfs-2.0.1# glusterfs –version
glusterfs 2.0.1 built on May 29 2009 17:23:10
Repository revision: 5c1d9108c1529a1155963cb1911f8870a674ab5b
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.
server1:/tmp/glusterfs-2.0.1#

Next we create a few directories:

mkdir /data/
mkdir /data/export
mkdir /data/export-ns
mkdir /etc/glusterfs

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 (192.168.0.102 = 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 192.168.0.102
  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. 192.168.0.102,192.168.0.103).

Afterwards we create the system startup links for the glusterfsd init script…

update-rc.d glusterfsd defaults

… and start glusterfsd:

/etc/init.d/glusterfsd start

3 Setting Up The GlusterFS Client

client1.example.com:

On the client, we need to install fuse and GlusterFS. Instead of installing the libfuse2 package from the Debian repository, we install a patched version with better support for GlusterFS.

First we install the prerequisites again:

aptitude install sshfs build-essential flex bison byacc libdb4.6 libdb4.6-dev

Then we build fuse as follows (you can find the latest patched fuse version on ftp://ftp.zresearch.com/pub/gluster/glusterfs/fuse/):

cd /tmp
wget ftp://ftp.zresearch.com/pub/gluster/glusterfs/fuse/fuse-2.7.4glfs11.tar.gz
tar -zxvf fuse-2.7.4glfs11.tar.gz
cd fuse-2.7.4glfs11
./configure
make && make install

Afterwards we build GlusterFS (just like on the server)…

cd /tmp
wget http://ftp.gluster.com/pub/gluster/glusterfs/2.0/LATEST/glusterfs-2.0.1.tar.gz
tar xvfz glusterfs-2.0.1.tar.gz
cd glusterfs-2.0.1
./configure –prefix=/usr > /dev/null

make && make install
ldconfig
glusterfs –version

… and create the following two directories:

mkdir /mnt/glusterfs
mkdir /etc/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

client1:/tmp/glusterfs-2.0.1# mount
/dev/sda1 on / type ext3 (rw,errors=remount-ro)
tmpfs on /lib/init/rw type tmpfs (rw,nosuid,mode=0755)
proc on /proc type proc (rw,noexec,nosuid,nodev)
sysfs on /sys type sysfs (rw,noexec,nosuid,nodev)
udev on /dev type tmpfs (rw,mode=0755)
tmpfs on /dev/shm type tmpfs (rw,nosuid,nodev)
devpts on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=620)
fusectl on /sys/fs/fuse/connections type fusectl (rw)
/etc/glusterfs/glusterfs.vol on /mnt/glusterfs type fuse.glusterfs (rw,max_read=131072,allow_other,default_permissions)
client1:/tmp/glusterfs-2.0.1#

… and…

df -h

client1:/tmp/glusterfs-2.0.1# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda1              29G  935M   27G   4% /
tmpfs                 126M     0  126M   0% /lib/init/rw
udev                   10M   80K   10M   1% /dev
tmpfs                 126M     0  126M   0% /dev/shm
/etc/glusterfs/glusterfs.vol
19G  804M   17G   5% /mnt/glusterfs
client1:/tmp/glusterfs-2.0.1#

(server1.example.com and server2.example.com each have 19GB of space for the GlusterFS filesystem, but because the data is mirrored, the client doesn’t see 38GB (2 x 19GB), but only 19GB.)

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

server1:~# ls -l /data/export
total 0
-rw-r–r– 1 root root 0 2009-06-02 15:31 test1
-rw-r–r– 1 root root 0 2009-06-02 15:32 test2
server1:~#

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

server2:/tmp/glusterfs-2.0.1# ls -l /data/export
total 0
-rw-r–r– 1 root root 0 2009-06-02 15:31 test1
-rw-r–r– 1 root root 0 2009-06-02 15:32 test3
-rw-r–r– 1 root root 0 2009-06-02 15:33 test4
server2:/tmp/glusterfs-2.0.1#

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

server1.example.com:

ls -l /data/export

server1:~# ls -l /data/export
total 0
-rw-r–r– 1 root root 0 2009-06-02 15:31 test1
-rw-r–r– 1 root root 0 2009-06-02 15:32 test2
server1:~#

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/

client1:~# ls -l /mnt/glusterfs/
total 0
-rw-r–r– 1 root root 0 2009-06-02 15:31 test1
-rw-r–r– 1 root root 0 2009-06-02 15:32 test3
-rw-r–r– 1 root root 0 2009-06-02 15:33 test4
client1:~#

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

server1:~# ls -l /data/export
total 0
-rw-r–r– 1 root root 0 2009-06-02 15:31 test1
-rw-r–r– 1 root root 0 2009-06-02 15:52 test3
-rw-r–r– 1 root root 0 2009-06-02 15:52 test4
server1:~#

 

  • GlusterFS: http://www.gluster.org/
  • Debian: http://www.debian.org/

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