overriding default scheduler for blkio requests in cgroups

I would really like to see you use RHEL/CentOS 6.3. Version 6.2 of EL was short-lived, and many of the bugfixes and enhancements were targeted for the release of newer point-release kernels. Red Hat/CentOS make this extremely clear, since there are NO updates for 6.2, and the packages are only available in the vault archive.

Either way, the tool you should make use of is the tuned and tuned-adm framework. Some of this is detailed here, in this question, with a more storage-focused answer here.

tuned-adm allows you to apply profiles to the system on-the-fly. Enabling a profile with: tuned-adm profile enterprise-storage, for instance, will apply the changes in the last column in the graph below; including remounting the filesystems with nobarrier and changing the I/O scheduler to deadline across the available block devices. Unfortunately, the virtual-guest profile only comes in EL 6.3 or newer... :( Another reason to upgrade...

In the end, tuned is a daemon, so it can be stopped/restarted on the fly. Just reload/reapply the service when a new FS is mounted. It will take care of the rest. You can also create your own profile with sysctl.conf and other performance settings...