Ext3

ext3 (third extended filesystem) is an open source disk filesystem created for Linux.

Kernel
Activate the following kernel options for ext3 support:

Support for optional ext3 features:

Large drive support
When the system has large disks (2 TB or greater) and a 32-bit kernel is being used, the following option must be enabled:

USE flags
The package contains the utilities to work with the filesystem. In Gentoo Linux is part of the system set and should be already installed on the system.

Emerge
After setting the USE flag update the system so the changes take effect: