A Hard disk drive is a permanent storage device used in a computer system. A HardDisk Drive or HDD consists of rotating platters of magnetic disks that store large amounts of data in a non-volatile or permanent state. That means that HDD data does not disappear when you turn off the computer.
Hard Disks are slower than main memory but faster than Optical drives. HDDs usually store the operating system and application software of a computer.
HDD capacity is measured in gigabytes or billions of bytes and in terabytes or trillions of bytes. The performance of an HDD is determined by a variety of factors including:
Revolutions Per Minute (RPM): How fast the platters spin per minute. The higher this number the faster a hard disk is. At the time of writing a 7200RPM hard disk would be the standard for desktop computers.
Cache: The amount of cache memory on-board the drive. The cache memory is used to store frequently accessed data. It is faster to deliver data from the cache than from the platters themselves.
Access time: Access time is the amount of time it takes to find and retrieve data from the hard disk. The lower the access time the faster the hard disk functions. Access time of 12-13ms is the norm for desktop hard drives at the time of writing.
Solid State Drive
A relatively recent invention, Solid State Drives (SSD) are a fast permanent storage device. SSDs use flash memory to store data quickly. SSDs are much faster than hard disk drives but are slower than main memory. SSDs are also more expensive than hard disk drives on cost per-gigabyte basis.
Because of their high cost SSDs aren’t as common as Hard disk drives. But prices are dropping fast and that should increase SSD adoption rates. SSDs usually come in 2.5″ form factor that requires the use of an adapter to get them to fit in a computer case. Some computer cases come with adapters built into them for SSDs.
SSDs do not have any moving parts in them so they make no noise whatsoever. This is another differentiating factor that separates SSDs with HDDs.
HDD capacity is measured in gigabytes or billions of bytes and in terabytes or trillions of bytes. The performance of an HDD is determined by a variety of factors including:
Revolutions Per Minute (RPM): How fast the platters spin per minute. The higher this number the faster a hard disk is. At the time of writing a 7200RPM hard disk would be the standard for desktop computers.
Cache: The amount of cache memory on-board the drive. The cache memory is used to store frequently accessed data. It is faster to deliver data from the cache than from the platters themselves.
Access time: Access time is the amount of time it takes to find and retrieve data from the hard disk. The lower the access time the faster the hard disk functions. Access time of 12-13ms is the norm for desktop hard drives at the time of writing.
Solid State Drive
A relatively recent invention, Solid State Drives (SSD) are a fast permanent storage device. SSDs use flash memory to store data quickly. SSDs are much faster than hard disk drives but are slower than main memory. SSDs are also more expensive than hard disk drives on cost per-gigabyte basis.
SSDs do not have any moving parts in them so they make no noise whatsoever. This is another differentiating factor that separates SSDs with HDDs.