The Storage Administration Guide contains extensive information on supported file systems and data storage features in Red Hat Enterprise Linux 6. This book is intended as a quick reference for administrators managing single-node (i.e. non-clustered) storage solutions.
1.1. What's New in Red Hat Enterprise Linux 6
Red Hat Enterprise Linux 6 features the following file system enhancements:
File System Encryption (Technology Preview)
You can now encrypt a file system at mount using eCryptfs , which provides an encryption layer on top of an actual file system. This "pseudo-file system" allows per-file and file name encryption, which offers more granular encryption than encrypted block devices. For more information about file system encryption, refer to Chapter 12, Encrypted File System.
File System Caching (Technology Preview)
FS-Cache allows you to use local storage for caching data from file systems served over the network (e.g. through NFS). This helps minimize network traffic, although it does not guarantee faster access to data over the network. FS-Cache allows a file system on a server to interact directly with a client's local cache without creating an overmounted file system. For more information about FS-Cache, refer to Chapter 11, FS-Cache.
I/O Limit Processing
The Linux I/O stack can now process I/O limit information for devices that provide it. This allows storage management tools to better optimize I/O for some devices. For more information on this, refer to Chapter 18, Storage I/O Alignment and Size.
The ext4 file system is fully supported in this release. It is now the default file system of Red Hat Enterprise Linux 6, supporting an unlimited number of subdirectories. It also features more granular timestamping, extended attributes support, and quota journalling. For more information on ext4, refer to Chapter 7, The Ext4 File System.
 This feature is being provided in this release as a technology preview. Technology Preview features are currently not supported under Red Hat Enterprise Linux subscription services, may not be functionally complete, and are generally not suitable for production use. However, these features are included as a customer convenience and to provide the feature with wider exposure.
You are free to provide feedback and functionality suggestions for a technology preview feature before it becomes fully supported. Erratas will be provided for high-severity security issues.