HDD Mechanics, Electronics

Transcription

1 FUNDAMENTAL OF HARD DISK DRIVE TECHNOLOGY พ นฐานเทคโนโลย ฮาร ดด สก ไดรฟ HDD Mechanics, Electronics เทคโนโลย เคร องกล อ เล กทรอน กส ในฮาร ดด สก ไดรฟ Dr. Anakkapon Saenthon King Mongkut's Institute of Technology Ladkrabang

2 Hard Drive Physical Components

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4 A hard drive is composed of: Individual disks called platters mounted on a spindle Read/Write heads on actuator arms controlled by a stepper motor or a voice coil A case which protects and holds the above components

5 The platters are made of aluminum and are coated with a magnetic medium. 2 tiny read/write heads service each platter: One reads the top of the platter The other reads the bottom of the platter The magnetic coating is phenomenally smooth, because the heads actually float on a cushion of air above the platters, which spin at speeds between 3,500 and 15,000 rpm.

6 The distance between the read/write heads and the disk is less than the thickness of a fingerprint about 10 nanometer. This means that even a tiny dust particle on the platter would cause catastrophic damage to the drive. To avoid this, hard drives contain a filtered aperture to keep the air pressure equalized between the interior and the exterior of the drive.

7 Spindle Motor

8 Disk data storage apparatus and method using multiple head actuators

9 The platters are made of aluminum and are coated with a magnetic medium. 2 tiny read/write heads service each platter: One reads the top of the platter The other reads the bottom of the platter The magnetic coating is phenomenally smooth, because the heads actually float on a cushion of air above the platters, which spin at speeds between 3,500 and 10,000 rpm.

10 The distance between the read/write heads and the disk is less than the thickness of a fingerprint. This means that even a tiny dust particle on the platter would cause catastrophic damage to the drive. To avoid this, hard drives contain a filtered aperture to keep the air pressure equalized between the interior and the exterior of the drive.

11 Actuator Arms

12 Moving The Arms The read/write heads move across the platter on the end of actuator arms. There are 2 technologies to move the arms: I. Stepper Motor II. Voice Coil Stepper motor was the first technology. Today all hard drives use voice coil technology.

13 Stepper Motor Actuator

14 Stepper Motor Actuator Stepper motor moved the arms in fixed increments or steps. This early technology had several limitations because the interface between the motor and the actuator arm required the least possible slippage in order to ensure precise movements. The pointing of the arms became less precise over time.

15 Stepper Motor Actuator The physical deterioration caused data transfer errors. Heat deformation caused havoc with the stepper motor drives. Accessing the data written on a cold hard drive, became more difficult once it warmed up. The read/write heads could damage the platters if not parked when not in use.

16 Voice Coil Actuator Circuit for control Arm

17 Voice Coil Actuator All drives made today use a linear motor to move the actuator arms. The linear motor, more popularly known as voice coil motor, use a permanent magnet surrounding a coil on the actuator arm. When an electrical current passes, the coil generates a magnetic field that moves the actuator arm.

18 Voice Coil Actuator The direction of the actuator arm depends on the polarity of the electrical current passing through the coil. Since the coil and the arm never touch, there is no degradation in positioning accuracy over time. Voice coil drives automatically park the hard drives when the drive loses power.

19 Hard Drive Interfaces Over the years many interfaces existed for hard drives. Since 1990, ATA interface monopolized the hard drive market. ATA: Advanced Technology Attachment ATA drives come in 2 basic version: PATA: Parallel ATA SATA: Serial ATA PATA dominated the market for more than a decade, and has only seen competition from SATA since 2003.

20 Hard Drive Interfaces Over the years, several ATA standards were released, starting from ATA-1 up to ATA- 7 An important standard was ATA -2 were ATAPI was introduced. ATAPI (ATA Packet Interface) enabled non-hard drive devices such as CD-ROM drives to connect to the PC via the ATA controllers. Another important standard is ATA-7 were SATA was introduced.

21 Hard Drive Interfaces Parallel ATA (PATA) Back of Drive Serial ATA (SATA) Back of Drive

22 Cabling Parallel ATA PATA drives use one of two cables to connect the drive and the controller. Both have a 40 pin interface, but differ in the number of wires.

23 Jumpering PATA devices Because two devices can be connected to one controller via a single cable, you need to be able to identify the cable. The PATA standard identifies the two as the Master and the Slave. The jumpers on these drives determine these settings. If you have one hard drive, set the jumpers to master. If you have two hard drives, set one to master and one to slave.

24 Jumpering PATA devices Many PATA hard drives have another jumper called, Cable Select. As the name implies, the position on the cable determines which drive will be master and slave: master on the end, slave in the middle. For CS to work properly with 2 drives, both drives must be set as cable-select, and the cable itself must be a special cable-select cable.

25 Jumpering PATA devices

26 Jumpering PATA devices

27 Serial ATA Serial ATA addresses several PATA issues: PATA hard drive technology has reached the limit of what it can offer. There is a limit of 18 inches regarding the length of the IDE cable. You cannot hot swap a PATA drive. Since SATA sends data serially rather than parallel, you need less wires to do so 7 instead of 80 resulting in much thinner cabling.

28 Serial ATA The maximum length of the SATA cable is more than twice that of an IDE cable 1m instead of 18 inches. SATA drives are hot pluggable. This makes SATA drives a natural fit for Redundant Array of Independent Disks (RAID) technology on OSs that support it. Data passing through a SATA device can theoretically move 30 times faster than through a PATA device.

29 Serial ATA SATA is backwards compatible with current PATA devices by using a device called a SATA bridge. If your motherboard does not have SATA controller sockets, you can add these via a PCI card.

30 Cabling SATA Drives Connecting a SATA drive is easier than connecting a PATA one, as there are no master-slave or cable select configurations to do. This is possible because SATA supports only one drive per controller channel.

31 Serial ATA

32 Protecting Data Losing data can be one of the worst things that can happen in PCs. There are several methods how to set hard drives in order to provide data protection. The following are the most common setups: Disk Mirroring Disk Duplexing

33 Protecting Data: Disk Mirroring Disk Mirroring Instead of relying on a single hard drive, we can use 2 or more drives to store the data. You could install a specialized hard drive controller. This control will read and write data to two hard drives simultaneously. So the data on each drive would be identical. The primary drive is the one being used, while the mirror drive is not used unless the primary drive fails.

34 Protecting Data: Disk Duplexing Disk Duplexing Disk duplexing is similar to disk mirroring but provides better safety This is done by using separate controllers for each of the drives Also, disk duplexing is faster than disk mirroring since the data is not read/written twice by one controller.

35 Protecting Data

36 BIOS Support Every device in your PC needs BIOS support, and hard drive controllers are no exception. In the old days, you needed to enter CHS information in the CMOS whenever you installed a new ATA drive. Today this process still needs to be done, with the difference that it is much more automated.

37 BIOS Support

38 BIOS Support These are some typical CMOS settings which are related to hard drives: 1. Enabling and disabling hard drives 2. Determine which hard drives are set as Master, and which are set as slave. This applies only to PATA drives 3. Setting the hard drive boot priorities, in relation to other boot devices such as other hard drives, floppy drive and optical drives.

39 Hard Disk Drivers ATAPI drives get BIOS support from software drivers, even though they connect to the same controllers as PATA hard drives Also, if SATA controllers are not part of the chipset of the motherboard, they will require a device driver for installation purposes.

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