primary and secondary Flashcards
what is primary storage
is volatile and usually refers the RAM
what is secondary storage
refers to non volatile such as hard disk and external storage devices such as ssd
what are the 3 main components of a hard disk drive
tracks sectors and platters
disk drive details
Concentric tracks are created on a magnetic disk
Disk spins at high speed: 3,600 – 7,200rpm
Spinning platters are each read by drive heads
Data is read or written as sector moves under the head
magnetic storage devices
positive or negative polarization of magnetic particles creates a binary pattern on the disk
changes from positive to negative or vice versa creates EM pulses
each pulse is read as 1 everything else as 0
advantages of HDDS
more densely packed platters
smaller magnetic parts and read write heads making them more compact
what is disk latency
the time taken to read/write disk data
seek delay - the time the head takes to move across the disk
rotational delay - the time taken by the disk to move to the correct sector underneath the read/write head
how do cds work
a low powered laser detects the reflection from pits and lands
only a pit end deflects the laser light and is read as a binary one
what formats are disks available as
read only
recordable
re-writeable
how do recordable formats detect pits and lands
use a transparent dye that becomes opaque when heated by a laser
how do re-writable formats detect pits and lands
use a laser to change the state of a phase-change alloy and a magnet to set the new state
NAND flash memory cells
contain no moving parts
floating gate transistors trap and store a charge
electron trapped inside the middle layer reads as a 0
outside the middle layer is read as a 1
ssd
comprises of millions of NAND flash memory cells
advantages of ssd
faster access speed as there is no moving read write head
lower power consumption
less suspectable to damage
silent
lighter
hard disk capacity
512 gb to 1tb
