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Chapter 4: Secondary Storage - Coggle Diagram
Chapter 4: Secondary Storage
Storage
RAM: Primary storage
Its contents whenever power is disrupted.
Secondary storage: provide nonvolatile storage.
Secondary storage devices: process of saving information is writing.
Important characteristics:
Media- actual physical material that retains data & programs.
Capacity- how much a particular storage medium can hold.
Storage devices: hardware that reads & writes to storage media.
Access speed- time required to retrieve data from a secondary storage device.
Hard Disks
Platters: provide a large amount of capacity.
Files are organized according:
Tracks- concentric rings on the platter.
Sectors- wedge-shaped sections.
Cylinders- run through each track of a stack of platters.
Density: how tightly electromagnetic charges can be packed next to one another on the disk.
Head crash: hard disk makes contact with the drive's read-write heads.
2 types:
Internal hard disk- located within the system unit.
External hard drives- removable.
Performance enhancements
Disk caching- provides a temporary high-speed holding area between a secondary storage device & the CPU.
RAID(redundant array of inexpensive disks)- several inexpensive hard-disk drives are connected together.
File compression & decompression- files are compressed before storing & then decompressed before being used again.
Solid state storage
Have no moving parts, provide access to flash memory.
Solid-state drives: similar to internal hard-disk drives expect they use solid-state memory, faster, more durable, more expensive & provide less capacity.
Flash memory cards: small solid-state storage devices that are widely used with portable devices.
USB Drives: very small that they fit onto a key ring.
Optical discs: use laser technology.
The most widely used:
Compact discs (CDs): typical storage 700 MB. Used to store music.
Digital versatile discs (DVDs): standard optical discs. Typical storage 4.7 GB & used to store movies & software.
Blu-ray discs (BDs): designed to store hi-def (high-definition) video, typical storage 25 GB. Used to store hi-def video & video games.
Read-only (ROM for read-only memory) discs cannot be written on or erased by the user.
Write-once (R for recordable) discs can be written on once.
Rewritable (RW for rewritable or RAM form random access memory) discs are similar to write-once discs.
Cloud storage
Cloud storage (online storage): supplied by these servers.
Cloud servers provide storage, processing & memory.
Advantages for users include less maintenance, fewer hardware upgrades, & easy file sharing & collaboration.
Disadvantages for users include slower access speed & less control over file security.
Mass storage devices
Mass storage: tremendous amount of secondary storage required by large organizations.
Mass storage devices: specialized high-capacity secondary storage devices.
Enterprise storage system: most large organizations.
Disaster recovery specialists: responsible for recovering systems & data after a disaster strikes an organization.