Introduction to hard disk drive Conference 2

1. Introduction to hard disk driveConference 2 From: Wikipedia, the free encyclopedia

2. Architecture • The motor has an external rotor; the stator windings are copper-colored. • The spindle bearing is in the center. • To the left of center is the actuator with a read-write head under the tip of its very end (near center); the orange stripe along the side of the arm, a thin printed-circuit cable, connects the read-write head to the hub of the actuator. • The flexible, somewhat 'U'-shaped, ribbon cable barely visible below and to the left of the actuator arm is the flexible section, one end on the hub, that continues the connection from the head to the controller board on the opposite side.

3. Architecture • The head support arm is very light, but also rigid; in modern drives, acceleration at the head reaches 250 g's. • The silver-colored structure at the upper left is the top plate of the permanent-magnet and moving coil "motor" that swings the heads to the desired position. • Beneath this plate is the moving coil, attached to the actuator hub, and beneath that is a thin neodymium-iron-boron (NIB) high-flux magnet. • That magnet is mounted on the bottom plate of the "motor".

4. Architecture • The coil, itself, is shaped rather like an arrowhead, and made of doubly-coated copper magnet wire. • The inner layer is insulation, and the outer is thermoplastic, which bonds the coil together after it's wound on a form, making it self-supporting. • Much of the coil, sides of the arrowhead, which points to the actuator bearing center, interacts with the magnetic field to develop a tangential force to rotate the actuator. • Considering that current flows (at a given time) radially outward along one side of the arrowhead, and radially inward on the other, the surface of the magnet is half N pole, half S pole; the dividing line is midway, and radial.

5. Capacity and access speed • Using rigid disks and sealing the unit allows much tighter tolerances than in a floppy disk drive. • Consequently, hard disk drives can store much more data than floppy disk drives and can access and transmit it faster.

6. Capacity and access speed • As of January 2008: • A typical desktop HDD, might store between 120 and 300 GB of data (based on US market data[10]), rotate at 7,200 revolutions per minute (RPM) and have a media transfer rate of 1 Gbit/s or higher. (1 GB = 109 B; 1 Gbit/s = 109 bit/s) • The highest capacity HDDs are 1 TB[11].

7. Capacity and access speed • The fastest “enterprise” HDDs spin at 10,000 or 15,000 rpm, and can achieve sequential media transfer speeds above 1.6 Gbit/s.[12] Drives running at 10,000 or 15,000 rpm use smaller platters because of air drag and therefore generally have lower capacity than the highest capacity desktop drives. • Mobile, i.e., laptop HDDs, which are physically smaller than their desktop and enterprise counterparts, tend to be slower and have less capacity. A typical mobile HDD spins at 5,400 rpm, with 7,200 rpm models available for a slight price premium. Because of the smaller disks, mobile HDDs generally have lower capacity than the highest capacity desktop drives.

8. Capacity and access speed • The exponential increases in disk space and data access speeds of HDDs have enabled the commercial viability of consumer products that require large storage capacities, such as digital video recorders and digital audio players.[13] In addition, the availability of vast amounts of cheap storage has made viable a variety of web-based services with extraordinary capacity requirements, such as free-of-charge web search and email (Google, Yahoo!, etc.). • The main way to decrease access time is to increase rotational speed, while the main way to increase throughput and storage capacity is to increase areal density. A vice president of Seagate Technology projects a future growth in disk density of 40% per year.[14]Access times have not kept up with throughput increases, which themselves have not kept up with growth in storage capacity.

9. Capacity and access speed • As of 2006, some disk drives use perpendicular recording technology to increase recording density and throughput.[15] • The first 3.5" HDD marketed as able to store 1 TB was the Hitachi Deskstar 7K1000. It contains five platters at approximately 200 GB each, providing 935.5 GiB of usable space.[16] Hitachi has since been joined by Samsung (Samsung SpinPoint F1, which has 3 × 334 GB platters), Seagate and Western Digital in the 1 TB drive market.[17][18]

10. Capacity and access speed

11. Capacity measurements • The capacity of an HDD can be calculated by multiplying the number of cylinders by the number of heads by the number of sectors by the number of bytes/sector (most commonly 512). • Drives with ATA interface bigger and more than eight gigabytes behave as if they were structured into 16383 cylinders, 16 heads, and 63 sectors, for compatibility with older operating systems.

12. Capacity measurements • Unlike in the 1980s, the cylinder, head, sector (C/H/S) counts reported to the CPU by a modern ATA drive are no longer actual physical parameters since the reported numbers are constrained by historic operating-system interfaces and with zone bit recording the actual number of sectors varies by zone. • Disks with SCSI interface address each sector with a unique integer number; the operating system remains ignorant of their head or cylinder count.

13. Capacity measurements

16. TSD-1000AS 1.Seagate Barracuda 7200.11 1TB Hard Drive - 7200RPM, 32MB, SATA-300, OEMCombining proven components, state-of-the-art technology and expertise in volume manufacturing, the Seagate® Barracuda 7200.11 drive Related Products in Category: 400 - 1000 GBManufacturer: Seagate