Module 4: Intelligent Storage Systems (Components) Flashcards
(40 cards)
What are the two key functional components of ISS?
disk controller
storage device
What are the characteristics of a storage controller in an ISS?
ISS typically has more than one controller
controller has one of more processors and cache memory for IO requests
connected to compute system either directly or through storage network
How do storage controllers work in an ISS?
receive IO requests from compute system that are read or written from or to storage by the controller
What is a hard disk drive?
persistent storage device that uses rapidly spinning disk or platter coated in magnetic material to store data
How are IO operations performed on an HDD?
performed by rapidly moving arm across spinning disks/platters
How is data transferred in an HDD?
done between disk controller and platters through read/write head attached to the arm
How is data recorded on a platter?
recorded on binary code
What is a head disk assembly (HDA)?
case that the set of platters is in
How is data encoded onto the platter?
polarizing magnetic material on both sides of the platter - data can be written/read on both sides also
What determines drive capacity?
number of platters
storage capacity of each platter
What is a spindle?
connects all platters together - connected to the motor which rotates at constant speed
What is RPM in an HDD?
rotations per minute
How does the R/W Head work?
senses magnetic polarization but never touches platter - maintains microscopic air gap in between called “head flying height”
air gap removed when spindle stops spinning and R/W head rests on landing zone
How are R/W Heads mounted?
on the actuator arm assembly - positions R/W Head on part of platter where data must be read or written
R/W heads for all platters are attached to one actuator arm assembly and move across platters simultaneously
What is the controller in an HDD?
printed circuit board mounted at the bottom of the drive
What are the parts of the controller in an HDD?
microprocessor
internal memory
circuitry
firmware
What does the firmware do in the drive controller?
controls power and speed motor
manages communication between drive and compute system
controls R/W operations - moves actuator arm and switches between different R/W heads
What are the factors that affect drive performance?
seek time
rotational latency
data transfer rate
What is seek time?
time it takes to position R/W heads across platter with a radial movement
aka time taken to position and settle arm and head over the write right track
What is the relationship between seek time and performance?
lower the seek time the faster the IO operation
What is rotational latency?
time taken by the platter to rotate and position data under the R/W head
How is data accessed on a HDD?
actuator arm moves R/W head over platter to particular track
platter spins to position requested sector under R/W Head
What is rotational latency dependent on?
rotation speed of spindle - measured in milliseconds
How is a read operation performed on an HDD?
data first moves from disk platter to R/W heads - than moves to drives internal buffer
data moves from buffer through the interface to the HBA on compute system
