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ISM v5 > Module 4: Intelligent Storage Systems (Components) > Flashcards

Module 4: Intelligent Storage Systems (Components) Flashcards

1
Q

What are the two key functional components of ISS?

A

disk controller
storage device

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2
Q

What are the characteristics of a storage controller in an ISS?

A

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

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3
Q

How do storage controllers work in an ISS?

A

receive IO requests from compute system that are read or written from or to storage by the controller

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4
Q

What is a hard disk drive?

A

persistent storage device that uses rapidly spinning disk or platter coated in magnetic material to store data

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5
Q

How are IO operations performed on an HDD?

A

performed by rapidly moving arm across spinning disks/platters

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6
Q

How is data transferred in an HDD?

A

done between disk controller and platters through read/write head attached to the arm

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7
Q

How is data recorded on a platter?

A

recorded on binary code

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8
Q

What is a head disk assembly (HDA)?

A

case that the set of platters is in

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9
Q

How is data encoded onto the platter?

A

polarizing magnetic material on both sides of the platter - data can be written/read on both sides also

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10
Q

What determines drive capacity?

A

number of platters
storage capacity of each platter

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11
Q

What is a spindle?

A

connects all platters together - connected to the motor which rotates at constant speed

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12
Q

What is RPM in an HDD?

A

rotations per minute

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13
Q

How does the R/W Head work?

A

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

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14
Q

How are R/W Heads mounted?

A

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

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15
Q

What is the controller in an HDD?

A

printed circuit board mounted at the bottom of the drive

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16
Q

What are the parts of the controller in an HDD?

A

microprocessor
internal memory
circuitry
firmware

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17
Q

What does the firmware do in the drive controller?

A

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

18
Q

What are the factors that affect drive performance?

A

seek time
rotational latency
data transfer rate

19
Q

What is seek time?

A

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

20
Q

What is the relationship between seek time and performance?

A

lower the seek time the faster the IO operation

21
Q

What is rotational latency?

A

time taken by the platter to rotate and position data under the R/W head

22
Q

How is data accessed on a HDD?

A

actuator arm moves R/W head over platter to particular track

platter spins to position requested sector under R/W Head

22
Q

What is rotational latency dependent on?

A

rotation speed of spindle - measured in milliseconds

23
Q

How is a read operation performed on an HDD?

A

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

23
Q

What is data transfer rate?

A

average amount of data per unit time that the drive can deliver to the HBA

23
Q

How is disk service time calculated?

A

seek time + rotational latency + data transfer rate

24
Q

How does disk controller utilization impact IO response time?

A

As utilization grows response time slows - IO requests become serialized in a waiting line - completed one at a time in order

25
Q

What are SSDs?

A

devices that use non-volatile flash storage for persistent storage - available with same interface as HDDs but consume less power

26
Q

What are the internal components of an SSD?

A

IO Interface
Controller
Mass Storage

27
Q

What is the IO Interface in an SSD?

A

connects the power and data connectors to the SSDs

28
Q

What is the controller in an SSD?

A

manages all drive functions - consists of drive controller, RAM and NVRAM

29
Q

What is the NVRAM in an SSD controller used for?

A

to store the SSDs operational data and software - not all SSDs have separate NVRAM

30
Q

What is the RAM in an SSD controller used for?

A

used in management of data being read and written from the SSD as a cache and for SSDs operational data and software

31
Q

What is mass storage in an SSD controller used for?

A

an array on nonvolatile memory chips - retains the contents when powered off - chips called flash memory - number of chips related to drive’s capacity

32
Q

What are some characteristics of SSD performance?

A

perform better random reads

use all internal IO channels in parallel for multi-threaded large block operations

best for workloads w/ short burst of IO activity

33
Q

What does SSD performance depend on?

A

access type
drive state
workload duration

34
Q

What is the effect of SSDs being random access devices?

A

SSDs pay no penalty for retreiving IO - gives them a much higher response time than HDD

35
Q

What effect does high capacity utilization have on SSDs?

A

take longer to complete read write cycle

36
Q

What is the best environment to run SSDs?

A

carefully tuned multithreaded small-block random IO workload storage environments

37
Q

What is the goal of Moore’s law when it comes to storage?

A

something that has the speed of DRAM but cost of NAND memory

ISM v5 (32 decks)

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