MGMT 104 Lecture Notes - Lecture 4: Direct-Access Storage Device, Holographic Versatile Disc, Optical Storage

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NOTES FOR 2/6/2017
Secondary Storage
Devices that store large amounts of data, instructions, and info more than allowed with memory
Advantages over memory:
Nonvolatility
Greater capacity and economy
Are not directly accessible by the CPU
Most common forms
Magnetic
Optical
Solid state
Access Methods
Sequential access
Data must be retrieved in the order in which it is stored
Devices used are called sequential access storage devices (SASDs)
Direct access
Records can be retrieved in any order
Devices used are called direct access storage devices (DASDs)
Magnetic Secondary Storage Devices
Magnetic tapes: a type of sequential secondary storage medium
Primarily for storing backups of critical organizational data
Hard disk drive (HDD): a direct access storage device; consists of rapidly rotating disks
coated with magnetic material
Redundant array of independent/inexpensive disks (RAID): a method of storing data
that generates extra bits of data from existing data
Disk mirroring: a process of storing data that provides an exact copy that protects users
fully in the event of data loss
Virtual tape: a storage device for less frequently needed data
Optical Secondary Storage Devices
A form of data storage that uses lasers to read and write data
Common types of optical storage devices
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Compact disc read-only memory (CD-ROM)
Digital video disc (DVD)
Blu-ray high-definition video disk
Holographic Versatile Disc (HVD)
DNA data storage: experimental at this time
Solid State Secondary Storage Devices (SSDs)
Store data in memory chips rather than magnetic or optical media
Advantages
Require less power and provide faster access than magnetic data storage devices
Have no moving parts, so they are less fragile than hard disk drives
A universal serial bus (USB) flash drive is a common SSD
Infrastructure as a Service (IaaS): A computing model in which an organization outsources
the equipment used to support its business operations, including storage, hardware, servers,
and networking components
The service provider owns the equipment and is responsible for housing, running,
and maintaining it
Enterprise Storage Options
Large secondary storage
Forms of enterprise storage
Attached storage: Includes devices connected directly to a single computer
Tape, HDDs including RAID devices, virtual tape, optical devices, and SSDs
Advantages: simple and cost effective for single users and small groups
Disadvantages: does not allow systems to share storage, and data backup is difficult
Network-attached storage (NAS): A HDD storage device that is set up with its own
network address and provides file-based storage services to other devices on the network
Common applications for NAS
Consolidated storage
Internet and e-commerce applications
Digital media
Storage area networks (SANs):A high-speed, special-purpose network that integrates
different types of data storage devices (e.g., HDDs, magnetic tape, SSDs) into a single
storage system and connects that to computing resources across an entire organization
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