SATA goes faster, Drives changing
September, 13, 2010, Intel Developer Forum San Francisco—the Serial ATA International Organization released the Serial ATA Revision 3.1 Specification. SATA 3.1 enables new capabilities and functions within the interface. This latest revision enables 6Gb/s link speeds between storage units, disk drives, optical and tape drives and protocol host bus adaptors (HBAs). At the same time, this specification is backward compatible with earlier SATA Implementations 1.5 and 3Gb/s in both hardware and software.
The spec now links power management capabilities on both sides of the interface, and allows optical drive to be powered down completely when not in operation. The PHY power management requirements are now mandatory on both ends of the interface. Additional power management features include the ability to stagger spin up of multiple drives and to unload heads. A web page http://www.serialata.org/technology/port_multipliers.asp has the animation for port multipliers, a function that uses the staggered power up function.
The Native Command Queuing (NCQ) streaming command enables asynchronous data transfers for bandwidth-hungry audio and video applications. The organization's website http://www.serialata.org/technology/ncq.asp has an animated slide showing how NCQ can speed up drive operations. The NCQ Management feature helps optimize performance by enabling host processing and management of outstanding NCQ commands.
All of these efforts to speed up the drive and interface, however, may be a negated by another announcement coming out of IDF. The IDEMA, an organization comprised of disk drive manufacturers http://idema.org/ , is announcing advanced format technology. Until now, HDDs were interfaced via a 512-byte physical sector size. Advanced format technology will change this to 4096-byte sectors. The change will enable continued storage capacity growth, increased format efficiencies, and better data integrity at higher densities.
For compatibility reasons, it is believed that the traditional 512-byte sector should continue to be exposed to the host. As long as file systems are properly aligned, no performance impact can be seen. If a file system is misaligned, a noticeable impact in performance can be observed. (See graphic.)
For large files and new files, the drives will be faster, enabling the drive to take advantage of the higher speeds from the SATA interfaces. If, however, you are rewriting data to the sector, the drive will need to make at least two passes to save your data. On the first pass, it will read the sector and calculate available space. On the second pass, it will write those data into the sector and, if necessary, write a jump link to the next available sector for overflow data.
The organization's website has a list of functions that can be affected by this change in formats. Basically, everything that can be stored on a hard drive is potentially going to be affected by this change to the sector sizes. These changes are going to phase in starting in January 2011.