It used to be called Advanced Technology Attachment with Packet Interface (ATA/ATAPI). ATA/ATAPI is the result of a long history of development. It is an evolution of the AT Attachment Interface, which was itself evolved in several stages from Western Digital's original Integrated Drive Electronics interface. As a result, many near-synonyms for ATA/ATAPI and its previous incarnations exist, including abbreviations such as IDE which are still in common informal use. With the market introduction of Serial ATA in 2003, the original ATA was retroactively renamed Parallel ATA (PATA).
Parallel ATA standards allow cable lengths up to only 18 inches (46 centimeters). Because of this length limit the technology normally appears as an internal computer storage interface.
For many years ATA provided the most common and the least expensive interface for this application.
As of 2007, it has largely been replaced by Serial ATA (SATA) in new systems.
Serial Attached SCSI
Serial Attached SCSI (SAS) is a technology designed to move data to and from computer storage devices such as hard drives and tape drives. It is a point-to-point serial protocol that replaces the parallel SCSI. SCSI first appeared in the mid 1980s in corporate data centers. SAS uses the standard SCSI command set. At present it is slightly slower than the final parallel SCSI implementation, but in 2009 it will double its present speed to 6 Gbit/s. This will permit much higher speed data transfers. The protocol is "downwards"-compatible with second generation SATA drives. These drives may be connected to SAS backplanes (controllers), but SAS drives can not be connected to SATA backplanes.
The SAS protocol is developed and maintained by the T10 technical committee of the International Committee for Information Technology Standards (INCITS) and promoted by the SCSI Trade Association (SCSITA).
The SAS connector is much smaller than traditional parallel SCSI connectors allowing for the small drives. SAS supports point data transfer speeds up to 3 Gbit/s, but is expected to reach 12 Gbit/s by the year 2012.
The physical SAS connector is available in several different variants:
All the Greatest Hits
All the Greatest Hits is an album from the band McFly. They released it on November 5, 2007 and it features all of McFly's UK singles. The album also includes 3 new songs: "The Heart Never Lies", "The Way You Make Me Feel" and "Don't Wake Me Up".
The Judas Kiss
"The Judas Kiss" is the fourth single off the album by rock band Metallica off their ninth studio album "Death Magnetic".
Death Magnetic
Death Magnetic is the ninth studio album by heavy metal band Metallica. The album was released September 12, 2008 with the hits "The Day That Never Comes", "Cyanide", "My Apocalypse", "The Unforgiven III", and "The Judas Kiss".
"Death Magnetic" was nominated for four Grammy awards. Rick Rubin won "Producer of the Year, Non-Classical" for his work on "Death Magnetic", as well as other albums this past year.
The album won two Grammys for "Best Metal Performance" and "Best Recording Package" at the 51st Grammy Awards on February 8, 2009.
Tagged Command Queuing
Tagged Command Queueing (TCQ) is a technology that allows to send multiple read and write requests to a hard drive simultaneously. ATA TCQ is not identical in function to the more efficient Native Command Queuing (NCQ) used by SATA drives. SCSI TCQ does not suffer from the same limitations as ATA TCQ.
Before TCQ, an operating system was only able to send one request at a time. In order to boost performance, it had to decide the order of the requests based on its own, possibly incorrect, idea of what the hard drive was doing. With TCQ, the drive can make its own decisions about how to order the requests (and in turn relieve the operating system from having to do so). The result is that TCQ can improve the overall performance of a hard drive if it is implemented correctly.
For efficiency the sectors should be serviced in order of proximity to the current head position, rather than in the order received. The queue is constantly receiving new requests and fulfilling and removing existing requests, and re-ordering the queue according to the current pending read/write requests and the changing position of the head. The exact reordering algorithm may depend upon the controller and the drive itself, but the host computer simply makes requests as needed, leaving the controller to handle the details.
This queuing mechanism is sometimes referred to as "elevator seeking", as the image of a modern elevator in a building servicing multiple calls and processing them to minimise travel illustrates the idea well.
If the buttons for floors 5, 2, and 4 are pressed in that order with the elevator starting on floor 1, an old elevator would go to the floors in the order requested. A modern elevator processes the requests to stop at floors in the logical order 2, 4, and 5, without unnecessary travel. Non-queueing disk drives service the requests in the order received, like an old elevator; queueing drives service requests in the most efficient order. This may improve performance slightly in a system used by a single user, but really comes into its own in a system with many users, making requests all over the disk surface.
Native Command Queuing
Native Command Queuing (NCQ) is a technology designed to increase performance of SATA hard disks on computers. It can do this under certain situations by allowing the individual hard disk to internally optimize the order in which it executes the read and write requests it received. This can reduce the amount of unnecessary drive head movement and resulting in better performance (and slightly decreased wear of the drive) for workloads where multiple read/write requests are outstanding at the same time. This situation most often occurs in server-type applications. However, the current (as of 2004) technology actually slows down HD access in certain applications, like games and sequential reads and writes, because of the added latency induced by NCQ logic.
Native Command Queuing was preceded by Parallel ATA's version of Tagged Command Queuing (TCQ). ATA's attempt at integrating TCQ was constrained by the requirement that ATA host bus adapters use ISA bus device protocols to interact with the operating system. The resulting high CPU overhead and negligible performance gain contributed to a lack of market acceptance for TCQ.
NCQ differs from PATA TCQ in that the command re-ordering is performed by the drive rather than the operating system, and each command is equal in importance. This is preferable since the drive has the most knowledge of its performance characteristics, and is able to take rotational position into account. NCQ and PATA TCQ have a maximum queue length of 32 in-flight commands (31 in practice), while SCSI TCQ has a maximum queue length of 2 in-flight commands.
For NCQ to be enabled, it must be supported and enabled in the SATA host bus adapter and in the hard drive itself. The appropriate device driver must be loaded into the operating system to enable NCQ on the host bus adapter. Many newer chipsets support the Advanced Host Controller Interface (AHCI), which should allow a generic driver supplied by the operating system to control them and enable NCQ. In fact, newer mainstream Linux kernels support AHCI natively. Unfortunately, Windows XP requires the installation of a vendor-specific driver even if AHCI is present on the host bus adapter. Windows Vista corrects this situation by including a generic AHCI driver.
Serial Storage Architecture
Serial Storage Architecture is a technology used to attach hard disks to Servers. It was developed by IBM in the 1990s. IBM produced a number of drives with this standard, but today, it has been largely replaced by the Fibre Channel architecture.
Fibre Channel