secondary storage- section 1 Flashcards
What is primary storage?
Primary storage refers to the memory areas that the CPU can access very quickly, like CPU registers, cache, ROM and RAM. Primary storage has the fastest read/write speeds and is mostly volatile.
What is secondary storage?
Secondary storage is non volatile- its where all data(operating systems, applications and user files) are stored when not in use. It includes magnetic hard disk drives, solid state drives, CDs and SD cards. Read write speeds are much slower compared to primary storage.
What are hard disk drives(HDDs)?
Hard disk drives are the traditional internal storage in PCs and laptops.
A hard disk drive is made up of a stack on magnetised metal disks spinning at a rate of between 5400 and 15000rpm(revolutions per minute).
How do HDDs work?
Data is stored magnetically in small areas called sectors within circular tracks. Read/write heads on a moving arm are used to access sectors on the disks.
Are they reliable?
Yes, HDDs are high capacity and despite their moving parts they are generally very long lasting and reliable, although they could be damaged by large impacts like being dropped.
Portable HDDs are popular for backing up and transporting large amounts of data.
What are solid state drives(SSDs)?
Solid state drives(SSDs) are storage devices with no moving parts. Most of them use a type of flash memory. They have the same purpose as HDDs- internal storage.
SSDs have significantly faster read/write times than HDDs. Using a SSD rather than a traditional HDD can give much quicker times for booting up and opening programs and files.
Hybrid devices exist which use solid state storage for the OS and programs, and a hard disk for data.
Like HDDs, portable SSDs can be used to back up and transport data.
What are the advantages of HDDs?
- HDDs are cheaper
- Both are high capacity but HDD is higher
- HDDs have longer read/write life than SSDs- SSDs can only be written a certain number of times before they begin to deteriorate.
What are the advantages of SSDs?
- SDDs are faster
- SSDs don’t need defragmentation
- SSDs are more shock proof than HDDs
- HDDs make some noise, SDDs are silent
What are optical discs?
Optical discs are things like CDs, DVDs and Blu-Ray discs. They come in three forms read only, write once, re writable.
How much data can a CD hold?
700MB
How much data can a DVD hold?
4.7GB
How much data can blu-rays hold?
25GB
Why is their use declining nowadays?
-As internet speeds have increased, streaming and downloading services like Netflix have removed the need for optical discs.
Modern devices like phones and tablets don’t have optical discs.
They have low storage, very slow read/write speeds and poor reliability.
But they are very cheap, portable and won’t be damaged by water or shocks but they can become scratched.
What are magnetic tapes?
Magnetic tapes are used by large organisations in archive libraries to store huge amounts of data.
It comes in plastic cassettes. Cassettes require a special tape for read/writing.
Tape is read/written sequentially, meaning it is read/written from the beginning till the end, or until it is stopped by the computer. This means that the tape is very slow when finding specific data stored on it, but it has a fast read/write speed once it is in the correct place to begin reading/writing.
Magnetic tapes has much greater storage capacity then HDDs, it also has an extremely low cost.
