They permanently store data unless they are formatted (deleting all information) or damaged.
Most hard disks will eventually fail..... It's just a matter of when. This is caused by the fast spinning platters and their close tolerances. You can view a wide range of hard drives here.
Since a hard drive's failure is imminent, it is extremely important to keep all your data backed up.
The hard disk drive is a non-volatile storage device to which your operating system, programs and files are stored. It is like an electronic filing cabinet.
Hard disks capacities are generally quoted in powers of 1000, hence a terabyte (TB) is 1000 gigabytes (GB), a gigabyte is 1000 megabytes (MB) and a megabyte is 1000 kilobytes (KB).
Computer file systems measure hard drive capacities in powers of 1024 thereby causing available disk space to be less than the advertised capacity.
On shutting down your computer, any information not saved on the hard drive will be lost.
These units are sealed to prevent the entry of dust and moisture.
For good performance, computer hard drives should be optimized which means increasing its storage space to the maximum.
Optimizing a hard drive increases its efficiency by speeding up disk operations and allowing more data to be stored on the disk. You can optimize your drive by:
Heat is a 'killer' of hard drives, therefore, it is mandatory that your hard drives are adequately cooled. Allow sufficient space around the drive for proper ventilation and, if necessary, install a hard drive cooler. You can view hard drive coolers here.
Never move your computer when the hard drive is running - you can damage the spinning platters inside the drive due to their close tolerances.
The structure of Computer Hard Drives
The first computer hard disk was invented by IBM in 1956 and their physical size and cost have reduced dramatically while capacity has increased.
Form factors have also changed over the period to today's popular 3.5 inch and 2.5 inch drives. 2.5 inch drives are mainly used in mobile and portable systems. There was also an unusual 1.8 inch form factor which is rarely used.
A hard drive has several platters that can store information on both sides. The platters are metal which are coated with a material that can be magnetically charged.
Earlier computer hard drives had approximately one or two platters (two or four sides). Today, large capacity drives have ten or more platters (twenty or more sides).
Older computers had hard drives with platters approximately 5 1/2 inches in diameter. The present hard drives have 3 1/2 inch diameter platters.
Portable computers or laptops have hard disks with 2 1/2 inches diameter platters. These platters are divided into circular rings called tracks and each track is divided into sectors.
One sector holds 512 bytes of data. The stacking of tracks on the platters produces a cylinder.
The read/write heads move together over the surface of the platters when reading or writing.
All the platters in the drive are formatted alike so that the tracks and sectors of each platter are identically aligned over each other. This causes the read/write heads to be always located over the same track and sector of each platter.
Seagate introduces 3TB External Hard Drive and announces first 1.5TB Portable Hard Drive
In the early '80s, computer hard disks had capacities of about 10MB (megabytes) which has drastically increased over the years to a 'whopping' 2TB (terabytes).
The massive Seagate STAC3000100 FreeAgent GoFlex Desk External Hard Drive offers a huge storage capacity of three terabytes (3TB) for your files.
With 3TB of space, you can fit all your files, digital library and backups on one drive! It uses the USB 2.0 interface for data transfer.
Today's disks have graduated from the slower IDE (PATA) Parallel ATA interface to the new serial interfaces namely, Serial ATA (SATA) and Serial attached SCSI (SAS).
SATA provides advantages over the older parallel ATA (PATA) interface such as smaller cables, reduced costs, faster and more effective data transfer and 'hot swapping'. 'Hot swapping' is removing and replacing the drive with the system powered on.
Computer Hard Drives - Capacity
The capacity of a hard drive is dependent on the following:
With the above factors, you can compute the capacity of the hard drive using the following formula:
Capacity = the number of sides
Computer Hard Drives - Speed
After capacity, the next most important feature of a hard drive is its speed.
The speed of computer hard drives is very important since the speed will affect the loading time of the programs that are used.
The drive speed is determined by data-encoding, rotational speed, speed of the read/write heads and the speed of data movement between the CPU and the drive.
Access time and seek time describes the speed at which the read/write head is moved to the correct point on the disk. Transfer time is the rate at which data is moved between the CPU and the disk.
Data transfer and seek time have dropped tremendously over the years due to advancements in technology.
In the SATA drive realm, Western Digital led the field in speed with its "Raptor 74GB, 10,000RPM SATA drive" which it has now increased to the new Raptor 150GB, 10,000RPM SATA drive.
This speed is still below the 15,000RPM boasted by "SCSI" drives.
Computer Hard Drives - Data Storage
Only a portion of the drive's surface is used for storing data. The first cylinder is reserved for the operating system files such as the File Allocation Table (FAT) and the Boot Record.
The remaining surface of the disk can be used for installing another operating system (dual boot) and your other programs and applications.
Reserved Disk Areas
The operating system designates some sectors of the disk for special functions which are listed below:
History of Computer Hard Drive Interface
The hard drive interface connects the drive to its controller. Below are the six different types:
Disk Rotation Speeds (RPM)These are the speeds (RPM) at which the internal disks within the hard drive rotate.
The first hard drive speed was 5400 RPM which eventually increased to 7200 RPM. The 5400 RPM hard drives are used mostly by laptops and older desktop PCs.
Most systems today use the 7200 RPM computer hard drives but you will also encounter the 10000 and the 15000 RPM drives in high-end systems. The 10000 and the 15000 RPM drives use the SCSI interface and are extremely fast but are expensive.
Serial ATAThe Parallel ATA drive is being replaced by the Serial ATA. This new drive offers more bandwidth than its predecessor and also enables easier installation. Easier means that it does not require jumper settings to configure it for Master or Slave or Cable Select; all Serial ATA Drives are equal.
SATA drives use smaller data and power cables as compared to the older flat ribbon cable used by parallel ATA drives. This allows increased air flow in computer systems.
Serial ATA interface allow data to be transmitted at a faster rate. This rate started out being 150MB/s which is a little faster than the old ATA drive which had a maximum rate of 133MB/s. The rate has now increased to 300MB/s and, hopefully, should reach 600MB/s by the year 2007.
Hard Drive TermsAreal Density: Areal Density or "Bit Density" is the amount of data that can be stored on a given surface area on the drive's platter. Hard drive performance can be enhanced by increasing the Areal Density.
Burst Speed: Hard drives contain internal memory which is called a "buffer". If data stored in this buffer is requested by the OS (operating system), it can be delivered right from the buffer which is faster than having the disk's mechanical system retrieve the data. This action of retrieving data from the memory is called "bursting" and the speed at which it delivers data from the memory or buffer is called the "burst speed". This internal memory or buffer is also referred to as "cache".
Hard drives are available in 2MB, 8MB, 16MB and 32MB cache.
S.M.A.R.T.: This stands for Self-Monitoring Analysis and Reporting Technology. This is a feature of hard drives which monitors the drive's overall condition and predicts the drive's life expectancy.
SSD (Solid-State Drives): Solid-State Drives are the new data storage devices that store data using solid-state memory. Click here for more information on SSDs (Solid State Drives).
With today's trend of drive capacities increasing while prices are decreasing, ”grab” the largest drive you can afford.
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