Here are main characteristics of Storage Devices.
Volatility of Information:
Memory can be volatile or non- volatile.
· Volatile Memory: These types of memory require constant power of operation, moment the power is off all data is written off For e.g. RAM.
· –Non-Volatile Memory: In this, data remain written even when power is off for e.g. hard disk.
· Dynamic Memory is also volatile memory but requires the stored information periodically to be refreshed.
Memory can be provide random or sequential access of required data.
· Random Access: In this type of access, the data can be accessed directly from its location; this type of access provides fast access of data.
· Sequential Access: In this, data can be accessed sequentially that one by one from its location.
Ability to change or read or write information:
Memory can be readable or writeable.
· Read / Write Storage: This type of storage allows both reading and writing of data e.g. hard disk.
· Read Only Storage: This type of storage allows only reading of data, that can be read the information from these storages, but we can not writeany thing on these storage for example: pre-written CD.
Type of address used for information:
Memory can use different types of addresses for data identifications.
· Location Address Storage: In this, Each Individual character of information is given separate address For example: RAM.
· File Address Storage: In this, Information is divided into files and file is provided an address e.g. Window Operating System provides a file addressable systems to users for easy accessibility of files, although the underlying system uses the location address system.
· Content Address Storage: This type of address system is implemented with the help of some software, to address a particular content or field. For Example: Mobile Memory for call log that missed call, received call,dialed calls etc is based on content address system.
Capacity and Performance:
Memory performance can be evaluated through followings:
· Storage Capacity: It is measured in megabytes (MB), gigabytes (GB), Terabytes (TB) etc.
· Storage Density: It is measured as Megabytes or Gigabytes.
· Latency: Latency is time taken to access the information from storage device. As we know, hard disk takes lesser time to access information than Floppy or CD. Latency is measured in milliseconds or microseconds.
· Throughput: It is the rate at which the information can be written or read from the storage device. It is measured in the MB/sec or GB/sec.