Mass Storage Devices

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Non-volatile storage devices hold data when the system is powered off.

• referred to as mass storage
• use magnetic, optical, or solid-state technology to store data

A mass storage device installed as an internal component is referred to as a fixed disk.

• produced in a number of standard widths:
  • 5.25 inches
  • 3.5 inches
  • 2.5 inches
• computer chassis has several drive bays to fit these form factors
• bays with a 5.25-inch width are provided with removable panels so that they can be used with devices that have removable media
  • DVD drives and smart card readers
• fixed disk is typically installed to a drive bay using a caddy
  • screw the drive into the caddy, then screw the caddy into the drive bay
  • can also allow you to fit a drive of a different size to the bay
  • Some caddies use rails so that you can pull the drive out without having to open the case

• Removable mass storage devices and removable media allow data to be archived and transferred between PCs
• External storage devices are also used for:
  • backup and data transfer
  • to provide a drive type not available as an internal unit
• an external hard drive is typically connected via a USB or Thunderbolt port
• common mass storage drive vendors
  • Seagate
  • Western Digital
  • Hitachi
  • Fujitsu
  • Toshiba
  • Samsung

Several factors impact the choice of mass storage devices:

• Reliability
  • concerns both the risk of total device failure and the risk of partial data corruption
  • Reliability and expected lifespan are rated by various statistics that are different for each technology type
• Performance
  • evaluate performance for the type of data transfer that the device will use predominantly
    • E.g., read and write performance have different characteristics
  • are also differences between
    • sequential access (reading data from the same “block” as might happen when transferring a large file)
    • and random access (reading data from different locations on the drive or transferring lots of small files)
  • data throughput measured in MB/s or GB/s
  • the number of input/output operations per second (IOPS) that can be achieved by a device for different kinds of data transfer operations
• Use
  • Examples of how storage is used include
    • running an OS
    • hosting a database application
    • streaming audio/video data
    • as removable media
    • and for data backup and archiving
  • use cases have different cost, reliability, and performance considerations