Storage Systems and Technologies, Study notes of Information and Communications Technology (ICT)

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Storage

1

Learning Objectives

1. Name several general properties of storage systems.
2. Describe the two most common types of hard drives and what they are used for today.
3. Discuss the various types of optical discs available and how they differ from each other.
4. Identify some flash-memory-based storage devices and media and explain how they are used today.
5. List at least three other types of storage systems.
6. Summarize the storage alternatives for a typical personal computer.

Storage System Characteristics

• (^) Can be internal, external, or remote
• (^) Are nonvolatile
• (^) Usually use random access; can be sequential
• (^) Logical file representation: The user’s view of

the way data is stored

• (^) Physical file representation: The actual

physical way the data is stored on the storage

media as viewed by the computer

Logical vs. Physical Representation

• (^) File: Anything stored on a storage medium, such as a program, document, digital image, or song
• (^) Filename: Name given to a file by the user
• (^) Folder: Named place on a storage medium into which files can be stored

Hard Drives

 Hard drive: Used to store most programs and

data

 (^) Can be internal and external

 Magnetic hard drives

 (^) Use metal hard disks  (^) Read/write heads magnetize particles to represent the data’s 0s and 1s

 Solid-state drives (SSDs)

 (^) Use flash memory technology  (^) Use less power and have no moving parts  (^) Particularly appropriate for portable computers

Magnetic Hard Drives

Solid State Drives (SSDs)

External Hard Drives

Hard Drive Cache

 Disk cache: Dedicated part of RAM used to store

additional data adjacent to data retrieved during

a disk fetch to improve system performance.

 (^) It works on the theory that neighboring data will likely have to be read soon anyway.  (^) So the computer reduces the number of disk accesses by copying such data into RAM early.  (^) When the next piece of data is requested, computer first checks the disk cache area. If data is not there, then data is retrieved from the disk.

 Saves time and reduces wear and tear on the disk.

 Extend battery life in portable computers.

Hybrid Hard Drives

Partitioning and File Systems

• (^) Partitions used to:
  • (^) Create a recovery partition
  • (^) Create a new logical drive for data
  • (^) Create a dual boot system (i.e. windows and Linux)
• (^) File system: Determines the cluster size,

maximum drive size, and maximum file size

• (^) FAT, FAT32, and NTFS

Partitioning and File Systems

Hard Drive Interface Standards

• (^) Common standards:
  • (^) Parallel ATA (PATA): older, slower standard
  • (^) Serial ATA (SATA)
  • (^) eSATA: uses USB or Firewire via expansion card for faster speeds
  • (^) SCSI and the newer serial attached SCSI (SAS)
  • (^) Fibre Channel
  • (^) Fibre Channel over Ethernet (FCoE)
  • (^) Internet SCSI (iSCSI)

Storage Systems for Large Computer Systems and Networks

• (^) Storage server: Hardware

device containing multiple

(array of) high-speed hard

drives

• (^) Businesses have to store

tremendous amounts of

data

• (^) Business data
• (^) Employee and customer data