InformationThe /var/log directory is used by system services to store log data .
There are two important reasons to ensure that system logs are stored on a separate partition: protection against resource exhaustion (since logs can grow quite large) and protection of audit data.
SolutionFor new installations, during installation create a custom partition setup and specify a separate partition for /var/log .
For systems that were previously installed, create a new partition and configure /etc/fstab as appropriate.
Resizing filesystems is a common activity in cloud-hosted servers. Separate filesystem partitions may prevent successful resizing, or may require the installation of additional tools solely for the purpose of resizing operations. The use of these additional tools may introduce their own security considerations.
AJ Lewis, 'LVM HOWTO', http://tldp.org/HOWTO/LVM-HOWTO/
When modifying /var/log it is advisable to bring the system to emergency mode (so auditd is not running), rename the existing directory, mount the new file system, and migrate the data over before returning to multiuser mode.