HDD's or Hard Drives usually refers to Hard Disk Drives. Hard disk drives play important role in a computer by storing all the informations of a user such as programs,documents,music etc. A computer system must have at least one Hard Drive or may have multiple drives. Hard drives have two positions in a computer system. A hard drive may be positioned internaly that is inside the computer or may be positioned externally that is outside the computer. In a computer system, a hard drive is the slowest part from all the parts of system. The size of a hard drive is measured in Gigabytes (GB).
Types of Hard Drives
Many types of hard disk drives are available today but the main types are few which are differentiate from each other according to their technological structure.
1)_ SCSI - These hard drives are the fastest hard drives uptill now. They are basically used in servers. SCSI are used in places where only the best reliability is needed. SCSI drives are highly expensive. Their speeds reach up to 320 MB/s.
2)_ SATA - SATA is a new era technology. SATA drives are becoming the standard for desktop computers. Their speeds reaches up to 375 MB/s. Because, SATA technology is latest therefore it can not work on older computers. A convertor card is used to use SATA technology in older computers. A SATA drive can be used either as internal and external drives depending upon the requirements of computer system. A computer may use internal SATA drive or may use external SATA drive.
3)_ IDE or PATA - This technology is in use for many years. Most systems of the last 15 years suppors this technology. PATA and IDE both refers to the same technology. Infact this technology is the replacement of the SATA. IDE hard drives reaches up to speeds of 133MB/s.
4)_ USB/ Fire wire - These technologies are used as external hard drives. USB2 is commonly used connection for an external hard drive. External hard drives generally slower than the internal hard drives. The max speed of Fire wire hard drives reaches up to 60MB/s.
Spin Speed
Besides the type of hard drives, the spin speed of hard drive also matters. The spin speed may vary from as slow as 4800 rpm to 15000 rpm. RPM is the ‘rotation per minute’. Usually the speed is measure in rpm. Slow spin speed as 4800 rpm is used in laptops and high spin speed as 15000 rpm is used in SCSI drives. The average spin speed of hard drive is 7200 rpm..
Cache Size
Cache size is also an important factor in hard drives. Usually, the hard drives have a cache of between 8MB to 16MB. The cache is a place where the data is temporarily stored before it is written to the hard disk. The cache is much faster than the drive itself.
Internal and external hard drives are manufactured by many manufacturers. The popular manufactures for hard drives are Maxtor, Western Digital, Seagate, IBM, FreeCom and LaCie.
