The 'advanced format' feature reduces overhead by using 4 kilobyte sectors instead of the traditional 512 byte sectors. The old format gave a format efficiency of 87%. Advanced Format results in a format efficiency of 96% which increases space by up to 11%. The 4k sector is slated to become the next standard for HDDs by 2014.
More Detailed Explanation
512-byte sector size standard is here for over 30 years and therefore lots of the code written for a Linux OS has 512 number hard coded in its source. The main idea in regards to the 4096 B size sectors is to increase the bit density on each track by reducing the number of gaps which hold Sync/DAM and ECC ( Error Correction Code ) information between each data sectors. Therefore, for 8 x 512 B sectors the track also holds 8 sector gaps.
By having one single sector of size 4096 B (8 x 512 B) the track holds only 1 sector gap for each data sector thus reducing an overhead for a need to support multiple Sync/DAM and ECC blocks and at the same time increasing bit density.
Linux partitioning tools by default start each partition on sector 63 which leads to a bad performance in HDDs that use this 4k sector size due to misalignment to 4K sector from the beginning of the track.
- Western Digital’s Advanced Format: The 4K Sector Transition Begins
- White paper entitled "Advanced Format Technology."
- Failure to align one's HDD results in poor read/write performance. See this article for specific examples.
Current HDD Models that Employ a 4k Sectors
As of July/2010, there are a limited number of HDDs that support "Advanced Format" or 4k sectors as shown below:
|Western Digital||WD20EARS||1.0 TB|
|Western Digital||WD15EARS||1.5 TB|
|Western Digital||WD00EARS||2.0 TB|