Search

It is recommended to read the WD Advanced Format Technology White Paper as an introduction to the technology. The key requirement for Advanced Format Drives to give their best performance is the alignment of partitions to match the 4KB boundaries of the drive's internal sectors.

For information about using Advanced Format Drives under Windows, refer to About WD Advanced Format Technology.

Mac OSX version 10.4 onwards (Tiger, Leopard and Snow Leopard) can use the GUID Partitioning Table scheme (GPT) which will align an Advanced Format drive correctly. Mac OS versions using Apple Partition Manager (APM) will not align partitions correctly and will not provide optimum performance.

Linux

Linux as an operating system is a combination of a kernel, user space utilities and customized packaging provided within the "distributions" such as Ubuntu, SuSE and Redhat.

The Linux kernel has had specific support for the alternate sector sizes and offsets used by WD Advanced Format disk drives since version 2.6.31. However, distributions based on Linux 2.6.34, the latest stable version of Linux, will provide the most thorough support. Advanced Format parameters are available in the sysfs file system from this kernel version onwards. Kernel versions older than 2.6.31 will not specifically detect Advanced Format Drives, but with proper alignment the system performance will be maintained. To ensure the best performance, it is important to:

• Align partitions to the internal 4KB sector boundaries of the drive.
• Make sure that data writes are aligned to 4KB sector boundaries.

Partitions are created by a number of possible utilities under Linux with "fdisk" and "parted" being typical command line tools. Parted is one of the better tools and from version 2.1 onwards it includes support for aligning Advanced Format drives. Fdisk and earlier versions of Parted won't automatically align partitions but can be used manually to set up the correct partition boundaries.

-a alignment-type, --align alignment-type 

valid alignment types are: 

         none              Aligns to 512 byte sector boundaries. 

         cylinder         Align partitions to cylinders. 

         minimal          Use minimum alignment: 4KB on AF drives 

         optimal          Use optimum alignment: 1MB boundaries  

If older versions of parted (pre 2.1) or fdisk are used to create partitions, a manual calculation of partition boundaries will ensure optimum performance of Advanced Format disk drives. The partitioning tool needs to be set t work in units of sectors rather than cylinders or Megabytes for example. Under parted, enter:

unit s

For fdisk, simply entering "u" will toggle between cylinder and sector mode. Make sure that all partitions start on a multiple of 8 sectors (8x 512B = 4KB) and that partition sizes are multiples of 8 sectors. Make sure that there is space left at the start of partitions as required. For example on a boot drive, do not start at sector 0 as there needs to be space for the boot code. Sector 64 is a good start point or even 2048 which would be a 1MB boundary. Also extended partitions will need a gap between their start point and the first logical partition contained within them.

The file system defaults on most Linux systems are to use blocks of 4KB data. Typically no specific actions are needed to configure block sizes for WD Advanced Format drives. For options on block sizes for the mkfs tools, consult the "man" pages. Note that for the e2fstools used for file system creation, version 1.41.10 onwards will warn the user that they are attempting to make a file system on an unaligned partition. The user is advised to repartition appropriately.

The installation defaults for Linux distributions create partitions based on pre-defined rule sets which may not allow for Advanced Format drive geometry optimisation. Current distributions will probably require manual setup of partitions as described above. Before running the installation process, access a command line terminal and create the required partitions using parted or fdisk. Once created, use the installer's option to install on existing partitions rather than create a new or modified partition table. Assume that distributions released in 2009 or earlier will not take account of Advanced Format drives.

Western Digital has been working with the Linux kernel development teams and with the vendors of the some of the more popular Linux distributions. Starting with Linux Kernel Version 2.6.34, the latest stable kernel release, the default installations will align partitions to the most appropriate boundaries on Advanced Format disk drives. For example, the following distributions will default to good alignment for Advanced Format disk drives: Ubuntu 10.04, Fedora 13, Redhat 6 and derived products. It is also expected that by release time Debian 6 (Squeeze) and openSUSE 11.3 will have completed the changes required for the default installation to be well aligned.

Linux users that build their systems from the Linux distribution should refer to the "ATA 4 KiB sector issues" article on the Kernel.Org ATA Wiki at: ATA 4KiB Sector Issues Article.