After reading http://af-design.com/blog/2009/02/27/amazon-ec2-disk-performance, I'm trying to do something new with my server. I want to use XFS for /var in my EC2. Why XFS ? you can read to this article : http://www.debian-administration.org/articles/388.

Updated!
Before you do this, backup all /var into /var-backup by sudo rsync -avr /var/* /var-backup/
After mounting EBS, you can rsync restore /var by sudo rsync -avr /var-backup/* /var/