Originally Posted by theYinYeti
That is good news! How did you do that, and with what filesystem?
You can increase the size of a logical volume whilst it is mounted, what you can't do is decrease the size whilst it is mounted
On RHEL (same for CentOS) go into system-config-lvm
Select the volume to be modified, and click Edit Properties.
Set the new size and click OK
If you are reducing the size, you will be told that the filesystem needs to be unmounted and asked if it's ok to unmount the filesystem and continue, if you are increasing it will just continue.
Just tested and increased size of / on the fly
You can even run df -k on the mount point and watch as the size is increased