Chapter 4. Technology Previews This chapter provides a list of all available Technology Previews in Red Hat Enterprise Linux 6.6. 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. Customers may find these features useful in a non-production environment. Customers are also free to provide feedback and functionality suggestions for a Technology Preview feature before it becomes fully supported. Errata will be provided for high-severity security issues. During the development of a Technology Preview feature, additional components may become available to the public for testing. It is the intention of Red Hat clustering to fully support Technology Preview features in a future release. 4.1. Storage and File Systems dm-era Device Mapper The device-mapper-persistent-data package now provides tools to help use the new dm-era device mapper functionality released as a Technology Preview. The dm-era functionality keeps track of which blocks on a device were written within user-defined periods of time called an era . This functionality allows backup software to track changed blocks or restore the coherency of a cache after reverting changes. dm-cache device-mapper Target The dm-cache device-mapper target, which allows fast storage devices to act as a cache for slower storage devices, has been added as a Technology Preview. See the lvmcache manual page for more information. Cross Realm Kerberos Trust Functionality for samba4 Libraries The Cross Realm Kerberos Trust functionality provided by Identity Management, which relies on the capabilities of the samba4 client library, is included as a Technology Preview starting with Red Hat Enterprise Linux 6.4. This functionality uses the libndr-nbt library to prepare Connection-less Lightweight Directory Access Protocol (CLDAP) messages. Package: samba-3.6.9-164 System Information Gatherer and Reporter (SIGAR) The System Information Gatherer and Reporter (SIGAR) is a library and command-line tool for accessing operating system and hardware level information across multiple platforms and programming languages. In Red Hat Enterprise Linux 6.4 and later, SIGAR is considered a Technology Preview package. Package: sigar-1.6.5-0.4.git58097d9 DIF/DIX support DIF/DIX, is a new addition to the SCSI Standard and a Technology Preview in Red Hat Enterprise Linux 6. DIF/DIX increases the size of the commonly used 512-byte disk block from 512 to 520 bytes, adding the Data Integrity Field (DIF). The DIF stores a checksum value for the data block that is calculated by the Host Bus Adapter (HBA) when a write occurs. The storage device then confirms the checksum on receive, and stores both the data and the checksum. Conversely, when a read occurs, the checksum can be checked by the storage device, and by the receiving HBA. The DIF/DIX hardware checksum feature must only be used with applications that exclusively issue O_DIRECT I/O. These applications may use the raw block device, or the XFS file system in O_DIRECT mode. (XFS is the only file system that does not fall back to buffered I/O when doing certain allocation operations.) Only applications designed for use with O_DIRECT I/O and DIF/DIX hardware should enable this feature. For more information, refer to section Block Devices with DIF/DIX Enabled in the Storage Administration Guide . Package: kernel-2.6.32-431 LVM Application Programming Interface (API) Red Hat Enterprise Linux 6 features the new LVM application programming interface (API) as a Technology Preview. This API is used to query and control certain aspects of LVM. Package: lvm2-2.02.100-8 FS-Cache FS-Cache in Red Hat Enterprise Linux 6 enables networked file systems (for example, NFS) to have a persistent cache of data on the client machine. Package: cachefilesd-0.10.2-1

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