Pascal Charest - blog d’un consultant en logiciel libre

Labs: installation & configuration of GlusterFS as synchronous data storage solution.
By: Pascal Charest, Freesoftware consultant
Date: September, 2008.

Synchronization of files in a cloud environment is a challenge in the path of high-{availability, performance}. From simple load balanced web sites to full-blown applications - some files always need to be in sync. Peoples, for simplicity, rely on asynchronous transfer (ie: rsync ), others deploy bigger solutions (ie: block device replication through DRBD or shared storage through AoE protocol & concurrency management with OCFSv2) or even go for the “lazy” “no-shared-storage” solution through NFS.

To address this problem in the PraizedMedia software stack, I decided to give FUSE based GlusterFS a try. Awesome, really ! The technical knowledge to deploy a basic solution is very very low. The modularity of the program also help to have “something working right now”. This isn’t meant as a direct alternative to DRBD or a good SAN deployment but in my use case, it fit perfectly.

In this lab, I will guide you through the installation of GlusterFS on 2 networked systems. They will be both used as “servers” & “client” for the GlusterFS filesystem. They will be sharing a directory (on both system : /var/production/brick), re-mounted as /var/production/static through GlusterFS. Any write I/O on this directory (of any client server) will be synchronized to the pool. This last feature is called “AFR” (for automatic file replication) and is a module (called a translator) to the GlusterFS file system.

The specificity of my environment is around the file-locking management : I don’t need any. By design, the application will never try to write the same file twice on any of the server.

#Installation of requirement (standard tools)
apt-get install flex bison libfuse-dev linux-headaers-`uname -r` curl

#download of the sources
cd /usr/local/src/
curl -O http://ftp.zresearch.com/pub/gluster/glusterfs/1.3/glusterfs-CURRENT.tar.gz
tar zxf glusterfs-CURRENT.tar.gz

# configure
cd glusterfs-1.3.11
./configure --prefix=/usr/local/glusterfs-1.3.11
make && make install
ln -s /usr/local/glusterfs-1.3.11 /usr/local/glusterfs

So we now have a basic 2 servers GlusterFS systems installed. Lets be honest, that wasn’t really hard! We are still missing configuration files though.

#Editing /usr/local/glusterfs/etc/glusterfs/glusterfs-server.vol
#
# glusterfs-servers definition
# volume definition are on first lvl, other are on second lvl (tabbed)
volume brick
type storage/posix
option directory /mnt/production/brick
end-volume

volume server
type protocol/server
option transport-type tcp/server
option auth.ip.brick.allow *
subvolumes brick
end-volume

#Editing the /usr/local/glusterfs/etc/glusterfs/glusterfs-client.vol
#
# glusterfs-client.vol
# volume definition are on first lvl, other are on second lvl (tabbed)
#
volume remote1
type protocol/client
option transport-type tcp/client
option remote-host 002.praized.com
option remote-subvolume brick
end-volume

volume remote2
type protocol/client
option transport-type tcp/client
option remote-host 001.praized.com
option remote-subvolume brick
end-volume

volume mirror0
type cluster/afr
subvolumes remote1 remote2
end-volume

#Launching services (servers and clients)
mkdir -p /mnt/production/brick
/usr/local/glusterfs-1.3.11/sbin/glusterfsd -f /usr/local/glusterfs-1.3.11/etc/glusterfs/glusterfs-server.vol

mkdir -p /mnt/production/static
/usr/local/glusterfs-1.3.11/sbin/glusterfs -f /usr/local/glusterfs-1.3.11/etc/glusterfs/glusterfs-client.vol /mnt/production/static/

You now possess a synchronized directory between your two systems. Please note that GlusterFS require TCP/6996 port to be open. There is also some improvement that can be done to this setup through adding a locking mechanism & i/o thread - I don’t currently need them, but you might.
Enjoy!

Debugging notes ; after starting the server process you should have a kernel process call glusterfs. All log files are in /usr/local/glusterfs/var/log/glusterfs*. After starting the client, “df -h” should show you your new mount point. Careful with UID/GID (&Permission), there is no such thing as root_squash_fs in GlusterFS yet.


Other notes ; Using Amazon EBS would have been the perfect solution if they did allow multiple servers-volume mount and lets us deal with concurrency / lock problems. But, they don’t.