HARD DISK Prabhavati M. (985450) Kamal Gidwani (962841) Sharvari Joshi (962281) Poonam Rode (985500) Rajesh S. (962206) )

What Is Hard Disk ?  HDD is a data storage device used for storing and retrieving digital information.  An HDD retains its data even when powered off.

History  1956: The drive holds 5MB of data at $10,000 a megabyte.  1963: The 1311, which has six 14- inch platters and holds 2.6MB.  1973: The 3340, the first modern "Winchester" hard drive, which has a sealed assembly, lubricated spindles and low-mass heads.  1978: First RAID technology patent is filed.

 1980: IBM introduces the first gigabyte hard drive.  1980: Seagate releases the first 5.25-inch hard disk.  1982: Western Digital announces the first single-chip Winchester hard drive controller (WD1010).  1992: Seagate comes out with the first shock-sensing 2.5-inch hard drive.  1992: Seagate is first to market with a 7200-revolutions-per-minute hard drive, the 2.1GB Barracuda.  1996: Seagate introduces its Cheetah family, the first 10,000-rpm hard drives.  2000: Seagate produces the first 15,000-rpm hard drive, the Cheetah X15.

 2003: Western Digital introduces the first 10,000-rpm SATA hard drive, the 37GB Raptor.  2006: Seagate releases the Barracuda , at 750GB.  2006: Western Digital launches its 10,000-rpm Raptor.  2010: Solid state hybrid drives is invented.

Storage Devices  Hardware that writes data to or reads data from a storage medium is called storage device.  Two primary storage technologies :  Magnetic storage  Optical storage

Why Hard Disk ?  Storage capacity  Data tranfer rate  Access time

Components Of Hard Disk

The hard drive, which typically provides storage for data and applications within a computer, has four key components inside its casing :  Platters  Spindle  Read/Write head  Actuator

Platters  A typical HDD design consists of a spindle that holds flat circular disks, also called platters, which hold the recorded data.

Platter’s Structure  Tracks  Sectors

Read/Write head  Read/Write head is used for read/write data in magnetic Form

Functionality  Platters are divided into billions of tiny areas.  Each one of those areas can be independently magnetized or demagnetized.  Magnetism is used in computer storage because it goes on storing information even when the power is switched off. If you magnetize a nail, it stays magnetized until you demagnetize it.

Dependencies  It depends on the rotational speed of a disk (or spindle motor), measured in revolutions per minute (RPM).  For most magnetic media-based drives, the average rotational latency is typically based on the empirical relation that the average latency in milliseconds for such a drive is one- half the rotational period.

Where HDD’s used ?  Desktop HDD’s  Mobile HDD’s  Enterprise HDD’s  Consumer electronics HDD’s

Visual Representation  Hard disk drives are traditionally symbolized as a stylized stack of platters.  They are shown by with a small lights to indicate data access.  HDD are represented by an illustration or photograph of drive enclosure.

File system 1. FAT (File Allocation Table) 2. NTFS (New Technology File System)

Interfaces :  They are three types of interfacing in hard disk  EIDE  PATA & SATA  SCSI

EIDE & PATA  It has a 40 pin connector.  Data transfer rate is 133mbps.  When installed this type of hard drives ensure that the jumpers are correctly configured.  If you have two devices connected to one IDE controller.

SATA  It has a 7pin connector.  It is the latest high-speed type of hard drive connectors.  Data transfer rate is 300mbps. As there are faster than old IDE interface.  The latest hard drives are using this type of interface.  As there are faster than old IDE interface.

SCSI  It has a 50 or 68 pin connector.  The data transfer rate is 600Mb/s.  These require a SCSI adapter card connected into the system.  Nowadays, most desktop computers did not use the SCSI.

Performance Characteristics Time to access data: The factors that limit the time to access the data on an HDD are mostly related to the mechanical nature of the rotating disks and moving heads. Seek time is a measure of how long it takes the head assembly to travel to the track of the disk that contains data. Latency Latency is the delay for the rotation of the disk to bring the required disk sector under the read-write mechanism. It depends on rotational speed of a disk, measured in revolutions per minute (rpm).

Data transfer rate  HDD data transfer rate depends upon the rotational speed of the platters and the data recording density.  Advancing density becomes the main method to improve sequential transfer rates.  Higher speeds require a more powerful spindle motor, which creates more heat. Other considerations  Other performance considerations include quality-adjusted price, power consumption, audible noise, and shock resistance.

Manufacturers and sales

Market updates  Global hard disk drive market have witnessed slight growth in 2014, as shipment of hard disk drives increased by ~2% as compared to previous year.  By type the global hard disk drive market can be segmented into internal hard drives and external hard drives.

Advanced Technologies  Shingled Magnetic Recording (SMR)  Two-Dimensional Magnetic Recording (TDMR)  Heat-Assisted Magnetic Recording(HAMR)  Hitachi has improved capacity in its top-end drives by filling them with helium.

Future development  High performance phase change memory/NAND hybrid solid state storage  New generations of Linear Tape -Open  IBM 154TB tape  Genetic storage

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