From 512B to 4K HDD sector size

Beginning end 2009 hard drive companies are migrating away from the legacy sector size of 512 bytes to a larger, more efficient sector size of 4096 bytes, generally referred to as 4K sectors, and now referred to as the Advanced Format by IDEMA (The International Disk Drive Equipment and Materials Association).

The structure of this sector layout was designed as follows:

• Gap section: The gap separates sectors.
• Sync section: The sync mark indicates the beginning of the sector and provides timing alignment.
• Address Mark section: The address mark contains data to identify the sector’s number and location. It also provides status about the sector itself.
• Data section: The data section contains all of the user’s data.
• ECC section: The ECC section contains error correction codes that are used to repair and recover data that might be damaged during the reading or writing process.

Each 512-byte sector has non-data-related overhead of 50 bytes for ECC and another 15 bytes for the Gap, Sync and Address Mark sections. This yields a sectorized1 format efficiency of about 88 percent (512/(512 + 65)).

The new Advanced Format standard makes the move to a 4K-byte sector, which essentially combines eight legacy 512-byte sectors into a single 4K-byte sector:

The Advanced Format standard uses the same number of bytes for Gap, Sync and Address Mark, but increases the ECC fi eld to 100 bytes. This yields a sectorized1 format effi ciency of 97 percent  4096/(4096 + 115)), almost a 10 percent improvement.

The most critical aspect of a smooth and successful transition to 4K sectors used in Advanced Format is to promote the use of 4K-aware hard drive partitioning tools. As a system builder, OEM, integrator, IT professional or even an end user who is building our configuring a computer, be sure to:
 

• Use Windows Vista (Service Pack 1 or later) or Windows 7 to create hard drive partitions.
• When using third-party software or utilities to create hard drive partitions, check with your vendor to make sure they are updated and confirmed to be 4K aware.
• If you have customers who commonly re-image systems, encourage them to make sure their imaging utilities are 4K aware.
• If you are using Linux, check with your Linux vendor or your engineering organization to make sure your system has adopted the changes to become 4K aware.
• Check with your hard drive vendor for any other advice or guidance on using Advanced Format drives in your systems.

The full article from Seagate can be found here.