01 - Section 1 - Secondary Storage Flashcards
What are the three tiers of storage?
Primary storage
Secondary storage
Tertiary storage
What is primary storage?
Primary storage refers to the memory that the CPU can access very quickly
- HAS THE FASTEST READ/WRITE SPEED
- MOSTLY VOLATILE
What are examples of primary storage?
CPU registers
cache
ROM
RAM
What is secondary storage?
It’s where all data (operating systems, applications and user files) are stored when not in use
- NON-VOLATILE
- READ/WRITE SPEEDS ARE A LOT SLOWER THAN PRIMARY
What are some examples of secondary storage?
Magnetic storage (e.g. HDD) Solid state storage (e.g. SD cards) Optical storage (e.g. CDs)
What is tertiary storage?
Tertiary storage is used for storing data more long term, used for archives and backups of masses of data
-NON-VOLATILE
What is an example of tertiary storage?
Magnetic tape library, which may use a robotic arm to access the tapes
What does HDD stand for?
Hard Disk Drive
What are HDDs made up of?
A stack of magnetised metal disks spinning at a rate between 5400 and 15000 rpm(revolutions per minute)
How is data stored on a HDD?
USED FOR INTERNAL STORAGE
Data is stored magnetically in small areas called sectors withing circular tracks.
Read/write heads on a moving arm are used to access the sectors on the disks
What is the use of a portable HDD?
-for backing up and transporting large amounts of data
What are SSDs?
USED FOR INTERNAL STORAGE
Storage devices with no moving parts
Most use flash memory
What are hybrid drives?
Drives which use Solid State Storage for the OS and programs and a Hard disk for data
What are types of flash storage?
USB pen drives
Memory cards (e.g. SD cards)
Flash based Solid-state storage
What are flash storage devices used for?
To expand the storage capacity of small devices (like cameras, smartphones, tablets)
-their capacity is relatively high relative to their size
What are the advantages of HDDs in comparison to SSDs?
- HDDs are cheaper
- both have high capacity but HDD is higher
- HDDs have a longer read/write life than SSDs (SSDs begin to deteriorate after a certain amount of times being written to)
What are the advantages of SSDs in comparison to HDDs?
- SSDs are faster
- SSDs don’t need fragmentation
- SSDs are more shock-proof than HDDs
- HDDs make some noise, SSDs are silent
What is storage media?
Storage media refers to the actual things that holds the data (e.g. optical disks)
What is a storage device?
A storage device is the thing that reads/writes data to media (e.g. HDDs or optical drive)
What are examples of optical disks?
CDs
DVDs
Blu-Ray
What are the three forms of optical discs?
- read-only (e.g. CD-ROM / DVD-ROM / BD-ROM
- write-once (e.g. CD-R / DVD-R / BD-R)
- rewritable (e.g. CD-RW / DVD-RW / BD-RW)
How is data stored on optical discs?
Data is stored as microscopic indentations on the shiny surface of the disc. Data is read by shining a laser beam on the surface and detecting changes in the position of the reflected beam
Why is the use of optical discs declining?
- internet speeds have increased, so streaming and downloading services (e.g. Netflix) have removed the need for optical discs
- modern phones, tablets don’t have an optical drive
- they used to be popular for backing up data but they can’t compete with flash storage
What is the use of magnetic tape?
Archiving (has a huge storage capacity and an extremely low cost per GB)
-used by large organisations in archive libraries to store huge amounts of data
How is data stored to magnetic tape?
Magnetic tape comes in cassettes which require special tape drives for read/writing
-tape is red/written sequentially (means tape is slow when finding specific data on it but it is fast once the correct place has been found)
What is the ranked order of secondary storage devices for their average read/write speed? (Fastest -> Slowest)
SSD HDD Magnetic tape memory card optical disc
What is the ranked order of secondary storage devices for their average cost per GB? (Priciest -> Cheapest)
SSD Memory card HDD optical disc magnetic tape
What is the ranked order of secondary storage devices for their average capacity? (Highest -> Lowest)
Magnetic tape HDD SSD Memory card Optical disc
What is the data capacity calculation for text files?
1 byte per character, + 10% for any overheads
What is the data capacity calculation for databases?
Step 1: How many bytes in 1 record.
Step 2: Multiply by the number of records
Step 3: Add 10% for overheads
What is the amount of memory different data types use?
-Text 1 byte per character -Integer 4/8 bytes -Real 4/8 bytes -Boolean 1 byte -Date 8 bytes
What is the data capacity calculation for images?
(Number of pixels * number of bytes per pixel) + 10% for overheads
What is the data capacity calculation for sound?
bytesPerSample * samplesPerSecond * channels * duration
