Advanced Format (AF) Drives
For General Users
Overview
Advanced Format (AF) Hard Disk Drives are used in many pre-built computers and USB drives from about 2011 onwards.. By way of explanation
- AF drives have 4 kB hard sectors in lieu of
- the traditional 512 B sectors
Advantages
- much faster (less disk overhead)
- more space efficient (larger disk capacity from same hardware)
- overcomes immutable capacity limit of ~2.19 TeraByte for conventional drives
Disadvantages
- Windows 32 bit systems cannot boot from AF drives
- requires driver from HDD manufacturer, to use as data only internal drives
No action is required by the typical purchaser, because the manufacturer will have taken care of the special formatting required with AF drives. Getting Technical below, provides guidelines for those needing to:
- repartition drives
- install new, "bare" drives
Getting Technical
Advanced Format Drives
New HDD from about 2011 onwards are likely to be Advance Formatted, whether obtained as part of a system, in an external case or as a "bare" new drive. AF drives are:
- usually pre-formatted
- likely to be stated on drive or packaging
- essential for drives over 2.19 TeraByte capacity
- has been used on new drives as small as 250GB
A new type of partition table called Globally Unique Identifier (GUID) Partition Table (GPT) is required to optimise the performance of AF disks. The partition table previously in common use has no universally agreed name but is given the nomenclature Master Boot Record (MBR), because that was a unique feature of it.
Windows & AF
GPT is not universally supported for all versions of Windows. Consequently AF drives night be poorly utilised. See http://www.microsoft.com/whdc/device/storage/GPT_FAQ.mspx
Legacy partitioning tools do not handle GPT. A suitable tool for intermediate users is "parted" or its GUI front-end "gparted". The simplest way to use these is from a bootable utility CD
http://www.sysresccd.org/Download
http://partedmagic.com/doku.php?id=downloads
Altering Partitions
It is not advisable to delete or alter partitions of type ef01 or ef02, because these have a special purpose in GPT. Other partitions may be re-sized or added, as required. Note that:
- all partitons in GPT are Primary
- up to 128 primaries are permitted
- GPT has no concept of "Extended" or "Logical" partitions.
- partition type numbers sometimes differ from those used with MBR partition tables
A compleat description of GPT is available at:
http://www.rodsbooks.com/gdisk
New Drives
The full capacity of Drives over 2.19 TB can be utilised only via recent mainboards or add-on SATA controllers. The technology transition point for recognising the full capacity is indistinct:
- SATA 3 (aka 6 Gb/sec) should
- newer SATA 2 (aka 3 Gb/sec) are likely to
The boot flag in GPT does *not* make a disk bootable from a BIOS mainboard. See the procedures at:
http://www.sysresccd.org/Sysresccd-Partitioning-EN-The-new-GPT-disk-layoutcoming soon
Re-formatting MBR
It is technically possible to reformat AF drives to MBR. This should be a last resort, used only to cope with older OS
- performance loss of up to 40% if reformatted MBR
- requires special procedure - see "Strictly for Geeks" below
Rpeters15:36, 6 September 2012 (EST)
