Types of storages. Primary storages of information. Examples
Types:
Primary or secondary
Volatile or non-volatile
Primary storage is electrical, resides on the bus, and is directly accessible to the processor.
Examples: Cache Memory - Describes a small amount of primary storage that is faster than the rest of the primary storage in a computer.
ROM - Read Only Memory retains its state in the absence of electrical power to hold the computer’s initial instructions.ROM devices do not change their state in response to an electronic signal; data must be burned into ROM memory using special equipment. Because of the expense of ROM and because data on ROM cannot be changed, computers contain only kilobytes of ROM compared to megabytes of RAM
RAM - Random Access Memory loses whatever data it has if someone turns off the computer without any data or programs in its memory the computer could not do anything when turned on.
Types of storages, secondary storages of information. Examples
Secondary storage is storage that the processor cannot access directly. When the processor needs data, it commands the controller to obtain the data from the secondary storage device and place it on the bus. The processor then uses the data immediately or keeps it in primary storage.
Types of storages. Volatile and non-volatile storages. Examples.
Volatile storage requires electrical power to retain its data.
Non-volatile storage retains its data even in the absence of electrical power.
27?28?29 – examples:
|
Primary |
Secondary |
Volatile |
RAM |
|
|
Cache |
|
Non-volatile |
ROM |
Disk |
|
|
Tape |
|
|
CD |
|
|
DVD |
|
|
Flash |
|
|
… |
Advantages of secondary storages over primary.
Access to data in secondary storage occurs at speeds several thousands to a million times slower than access to data in primary storage.
Much less expensive
Retains data without electrical power
Can be removed from its computer allowing the transfer of data between computers or the shipping of data as products
Types of storages. Distributed storage. Raid.
A storage area network (SAN) is a virtual storage device created by connecting different types of storage devices, over a high-speed network. A SAN centralizes storage so that any server connected to the SAN has access to its entire storage capacity.
A technology called RAID (redundant arrays of inexpensive disks) uses a large number of relatively small hard disks to create what appears to be a single storage device. RAID reduces the time required to read or write data because the computer can simultaneously read or write to each of the disks in the RAID array. RAID storage also takes significantly less room that conventional large disks.