SSD Characterization: From Energy … Characterization: From Energy Consumption's Perspective...

SSD Characterization:

From Energy Consumption's Perspective

Balgeun Yoo, Youjip WonSeokhei Cho, Sooyong Kang

Hanyang University

Jongmoo Choi

Dankook University

Sungroh Yoon

Korea University

HotStorage ‘11

June 14, 2011, Portland OR

Youjip Won Hanyang University HotStorage ’11, Portland, OR


Outline

Motivation

SSD Organization and Energy Consumption

Channels, Ways and Clusters

Case Study

Power Budget

Conclusion

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Motivation

3 /39


Motivation

Hard disk

Sector layout: cylinder serpentine vs. surface serpentine vs. hybrid

serpentine

Number of zones

Degree of track skew

Disk scheduling algorithm

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Understanding of Internal Mechanism of Storage Device is very important!


Characterizing HDD: Sector Layout

Jongmin Gim et al, ACM ToS 6, 2 (July 2010)

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Surface serpentine

Cylinder serpentineSpindleSpindle

Traditional SpindleSpindle SpindleSpindle

Zone rewind SpindleSpindle


Characterizing Storage Devices

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HDD Characterization is via measuring Seek time and Rotational Latency.

Characterizing SSD… what do we use?...


Motivation

What is available the number of channels

the number of chips/packages per channels

What is not available? Sector placement , Garbage collection algorithm

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How do we figure out the internals of SSD?


Operations on NAND Flash Cell

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Erased (1)Programmed (0)

Substrate

Source Drain

Floating Gate

Control GateOxide Layer

- - -

18~35V

Substrate

Source Drain

Floating Gate

Control Gate

- - -

program erase



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SSD Characterization

We will use “Energy Consumption”

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SSD Organization and Energy Consumption

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SSD Organization

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ControllerDRAM

I/OPhysical

Interface

Bus

Host Interface

NAND Flash Memory

Host


Characteristics of SSD Behavior

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=Page Write

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=Write Complete


IO Size vs. Energy Consumption

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Channels, Ways, and Clusters

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Writing 4 pages: 1 Channel X 1 Way

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Cur

rent

(mA

)

time

P

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=Page Write

C D

=Write Complete


Way switch vs. Channel switch Delay

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Cur

rent

(mA

)

time

=Page Write

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C D P

=Write Complete

Cur

rent

(mA

)

time

P

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C D

Way Switch Channel Switch

Way Switch Channel Switch



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Cur

rent

(mA

)

time

=Page Write

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C D P

=Write Complete



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Cur

rent

(mA

)

time

P

=Page Write

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C D

=Write Complete



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Cur

rent

(mA

)

time

P

=Page Write

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C D

=Write Complete

Way Switch

Channel Switch


Cluster

Cluster : Write Unit of SSD

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=Page Write

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=

4KB Write 8KB Write

Case Studies

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Measurement

Oscilloscope (TDS3032)

High resolution current probe(TCP202)

Current probe to power line(Vdd) of the

SSD

Sampling interval(10samples MA): 10usec

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Model Vendor Size Channels DRAM Size Package Type

X25M Intel 80GB 10 16MB 20 MLC

MXP SAMSUNG 128GB 8 128MB 16 MLC


Case Study : Intel X25M

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Capacity 80GB

No. of Channels 10

Packages/Channel 2

Package 4 GB

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NAND(4GB)

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IO Size: 4KB to 80KB

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100mA

17mA

Increase20 steps

Channel switch = 30 μsec

NAND programming: 17 mA

Simple Round Robin600 μsec



4KB to 80KB Sequential Write

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= Page Write

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0 2 3 4 5 6 7 8 91

10 121314151617181911

MUX

Channel Switch =30 μsec



80KB to 160KB Write

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80 KByte

84 KByte

?



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…

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=1 Page Write

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0 2 3 4 5 6 7 8 91

10 12131415161718191120

=Write CompleteMUX

time

P1P0

P2P3P4P5P6P7P8P9P10P11P12

P14P P13 P

P15P16

P19P18

P17

P20

Flo

w

time

Cur

rent


Case Study : SAMSUNG MXP

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NAND(8GB)

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Capacity 128GB

No. of Channels 8

Packages/Channel 2

Package 8 GB



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Peak Current

100mA50mA



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Same Peak Current



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Same Peak Current



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Cluster Size of MXP is 32KB

Same Peak Current



What we still do not know of

Peak of 128 Kbyte < Peak Current of 124 KByte

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Forth Coming Problem in Multi-channel SSD

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2008 2009 2010 2011

Read Write Capacity channel

Model Name Release

SATA3035 (Mtron) 2008.01

Vertex (OCZ) 2009.03

Vertex2 (OCZ) 2010.07

REVO Drive X2 (OCZ) 2011.01


Forth Coming Problem in Multi-channel SSD

10 channel: peak 500 mA

16 Channel: peak 800 – 900 mA SSD is no long Green.

Further, excessive peak current can cause…

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supply voltage drop

ground bounce

signal noise

black-out

Etc…


Power Budget

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Feasible Solutions

8 Channels X 1 Way

1 Channel X 8 Ways

Power Budget

Perfo

rmance B

ound

4 Channels X 2 Ways

2 Channels X 4 Ways

Power

I/O Latency

Feasible Region


Summary

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32KB

35mA

350mA

Cluster Size : 4KB

programming: 17 mA

Peak Current : 500mA

Channel switch: 30 μsec

MXPX25M

Energy

Performance

Small Write

Large write

Standby current


Summary

Energy Consumption is very good tool to characterizeSSD.

For larger number of channels, peak current will soon be a

significant issue.

We introduce the notion of Power Budge to resolve this

issue.

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Related Works

Dongkun Shin et al, NVRAMOS 2010 Spring

Laura M. Grupp et al, MICRO 2009

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Applied different workloads(random, sequential, etc) to SSDs andMeasured the power consumption

Read

Program

Erase

Custom Board+ Flash Memory

Basic Operation

Power Consumption of Flash Memory Basic Operations


Related Works

Euiseong Seo et al, HotPower’08

Vidyabhushan Mohan et al, Date ’10

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CACTI 5.3

developed a detailed power modelfor the NAND flash chip itself with CACTI 5.3

Applied different workloads(random, sequential, etc) to SSDswith different request sizes (varied the file systems)

Measured the Power Consumption



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ModelRead (mA)

Write (mA)

Erase (mA)

Voltage(V)

MD332B (Intel) 20 20 20 3.3

K9XXG08XXM (Samsung) 25 25 25 3.3

MT29FXXG08CXXBB (Micron) 20 20 20 3.3


Power Consumption of Storage Devices: System Boot

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stand-by current s

Active current of HDD

SSDs have various stand-by currents


FTL

FTL

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LPN: Logical Page Number PPN: Physical Page Number

LPN

PPN

0

12

1

11

2

10

3

1

4

3

5

7

Mapping Table

Flash Memory

Page 0 Page 8…

Block 0 Block 1 Block 2

Page FTL Block FTL

PBN: Physical Block Number

Hybrid FTL

Write toLPN = 5

Write toLPN = 3

LBN

PBN

0

5

1

1

2

7

Mapping Table

Flash Memory

Page 0 Page 8…


Write toLPN = 5

Write toLPN = 3

LBN = 1Offset =

2

Page 0 Page 8


Flash Memory

Write toLPN = 5

Write toLPN = 3

LBN = 1

LBN

PBN

0

5

1

1

2

7Block-Level

Mapping

LBN = 1Offset =

0

LPN

PPN

3

1

4 5

0Page-LevelMapping

Trivia in Measurement Methodology

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Trivia of Measurement Methodology

Sampling interval should be small enough.( Read/Program Latency)

Smoothing the data to filter out measurement noise.

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Smoothing

SSD Characterization: From Energy … Characterization: From Energy Consumption's Perspective...

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