Low Power Portable Storage

Love/Hate Relationship between Flash Memory and Microdrive for Low-Power Portable Storage 2004. 09. 26 Sang Lyul Min Seoul National University & Samsung Electronics

Agenda „ „ „ „

Overview of Portable Storage Technologies Techniques for High Performance Techniques for Low Power Conclusions

2

1

Portable Storage Applications

Source: http://www.samsung.com/AboutSAMSUNG/InvestorRelations/ IREvents/downloads/2003_samsungforum.pdf

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The Contenders for Portable Storage Market Flash Drive

Micro Drive IBM

Samsung

Hitachi

Toshiba Hitachi

Portable Storage SanDisk

Seagate

LexarMedia

4

2

Cost Comparison $399.95 (2004.8)

$299.88 (2004.8)

$259.88 (2004.8)

Source: http://www.hitachigst.com/hdd/technolo/overview/chart03.html 5

NAND Flash Memory Basics 2j blocks

Data

Spare

Data

Spare

Data

Spare

Data

Spare

Data

Spare

Data

Spare

Data

Spare

Data

Spare

Data

Spare

………

2i pages

… Data

„

„

… Spare

Data

Read physical page „ (chip #, block #, page #) „ ~ 25 us Write physical page „ (chip #, block #, page #) „ ~ 300 us

… Spare

Data

„

Spare

Erase block „ (chip#, block #) „ ~ 2 ms

6

3

FTL (Flash Translation Layer) „

„

Definition „ Software layer that makes flash memory appear to the system like a disk drive

Challenges in FTL „ Asymmetry in read and write speeds „ No overwrite is allowed without erasing 7

Logical interface for a disk drive 512B 512B

0

„

…

1

512B

N -1

Operations 1. Identify drive(): returns N 2. Read sectors(start sector #, # of sectors) 3. Write sectors(start sector #, # of sectors)

8

4

Block level mapping „

Logical blocks 0

1

N -1

…

Sectors

256 sectors

…

…

Logical blocks

… N / 256

0

9

Block level mapping „

Logical to physical block mapping Logical blocks Visible (data blocks)

…

… 0

Invisible

…

1

…

… L

…

Block mapping table (map block)

…

…

…

…

Physical blocks 10

5

Read procedure „

Ex. read 3 sectors from 255

Logical blocks

…

… 0

…

…

…

1

L

…

Block mapping table (map block)

…

…

…

R

R

…

R

Physical blocks

11

Write procedure (Data block update) „

Ex. write 3 sectors from 255 …

… 0

…

1

…

… L

…

Block mapping table (map block)

…

… … W

…

…

W W …

…

Write buffer blocks

Still, ofdata mapping information is needed 2. 1. 3.update Write Erase Fill remaining write pages buffer datablocks pages for data 12

6

Write procedure (Map block update) „

Ex. write 3 sectors from 255 …

…

… 0

…

…

1

L

…

Block mapping table (map block)

…

…

…

W

…

…

W W

…

…

W

Write buffer blocks

Still, somewhere we need to keep the addresses of 6.new Fillmap remaining mapblocks pagespage 4. 5. Erase Read-modify-write write buffer map for map and write buffer blocks (i.e., logging) 13

Inside Hard Disk Drive

CPU core

SRAM/DRAM System Bus

USB, PCMCIA, SATA

Host Interface

Platters

14

7

Host Interface Performance Transfer Rate (MB/s)

800

SAS6Gbps

700 S-ATA3

600 500 SAS3Gbps

400

Ultra320 SCSI S-ATA2

300

IEEE 1394b

200 100 SCSI-1

SCSI-2

SCSI-3

Ultra160 SCSI S-ATA1 IEEE 1394b IEEEUltra Ultra2 SCSI U-ATA66 USB 2.0 1394a SCSI U-ATA33 ATA2 ATA1 USB 1.1

19 86 19 87 19 88 19 89 19 90 19 91 19 92 19 93 19 94 19 95 19 96 19 97 19 98 19 99 20 00 20 01 20 02 20 03 20 04 20 05 20 06 20 07

0

IEEE 1394b

ATA

SCSI

SERIAL

15

HDD Form Factor and Capacity

Source: http://www.hitachigst.com/hdd/technolo/overview/chart01.html 16

8

HDD Internal Data Rate

Source: http://www.hitachigst.com/hdd/technolo/overview/chart16.html 17

Inside Flash Drive

CPU core

SRAM System Bus

USB, PCMCIA, SATA

Host Interface

Flash Interface

Flash Bus

Flash Chips

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9

Flash Chip Bandwidth „ „ „

Write bandwidth = 2KB/300us = 6.7MB/s per chip Read bandwidth = 2KB/25us = 80MB/s per chip Erase bandwidth = 128KB/2ms = 64MB/s per chip

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Flash bus bandwidth picture

20~33Mb/s per Pin

Flash

Source: Terry Lee, Micron Technology, Inc, VTF (VIA Technology Forum) 2003 20

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Agenda „ „ „ „

Overview of Portable Storage Technologies Techniques for High Performance Techniques for Low Power Conclusions

22

11

Techniques for High Performance Flash Drive CPU core

SRAM System Bus

High speed Flash bus

USB, PCMCIA, etc “Sleeping with the enemy”

Host Interface

Flash Interface

Flash Bus

“Getting out of the way” Flash Chips

Multiple logical chips in a single packaging (multi-banking)

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Techniques for High Performance HDD

Source: http://www.hitachigst.com/hdd/technolo/overview/chart19.html 24

12

Agenda „ „ „ „

Overview of Mobile Storage Technologies Techniques for High Performance Techniques for Low Power Conclusions

25

Literature on Power Modeling of Portable Storage „

„

„

IBM Corporation. Adaptive Power Management for Mobile Hard Drives. Technical Report, Storage Systems Division, IBM Corporation, April 1999. Available at: http://www.almaden.ibm.com/almaden/pbwhitepaper.pdf. John Zedlewski, Sumeet Sobti, Nitin Garg, Fengzhou Zheng, Arvind Krishnamurthy, and Randolph Wang. Modeling Hard-Disk Power Consumption. Proc. Second Conference on File and Storage Technologies. March 2003. Fengzhou Zheng, Nitin Garg, Sumeet Sobti, Chi Zhang, Russell E. Joseph, Arvind Krishnamurthy, and Randolph Y. Wang. Considering the Energy Consumption of Mobile Storage Alternatives. IEEE Symposium on Modeling, Analysis and Simulation of Computer Systems. October 2003.

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The Love Part: HDD+Flash Combo

+ HDD

=

HDD with reduced power consumption and start-up time

NAND Flash

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Why HDD+Flash Combo? 1.

Power consumption aspects: „

In a laptop PC, HDD consumes „ „

2.

Cost aspects: „

128MB Flash write buffer „ „

3. 4.

~10% (~2W) total power when disk platters are spinning ~1% (~0.2W) total power when disk platters are idle

< $8 in 2006 < $4 in 2008

Reliability aspects: Performance aspects:

Source: Clark Nicholson, “Improved Disk Drive Power Consumption Using Solid State Non-Volatile Memory”, WinHEC2004. 28

14

HDD+Flash Combo Block Diagram

CPU core

SRAM System Bus

Host Interface

SATA

Flash Interface

Flash Bus Flash Chip

Platters

29

Key Benefits of HDD+Flash Combo „ „

87% reduction in power can be achieved (1.75W) Assumptions „ Pavg active = ~2W (measured) „ Pavg with Flash write buffer and “Longhorn” kernel = 0.25W (calculated) „ „

Toff = 600s @ .18W Ton = 18s @ 2.5W „ Ton = spin up time (5s) + Flash buffer flush time (13s) „ „

Flash buffer size = 128MB Transfer rate = 10MB/s

Source: Clark Nicholson, “Improved Disk Drive Power Consumption Using Solid State Non-Volatile Memory”, WinHEC2004. 30

15

Key Considerations 1. 2.

3.

4.

5.

Correctness: should preserve the semantics of HDD Fault tolerance and graceful degradation: should operate correctly despite partial/total failure in flash memory Power efficiency: should reduce the power consumption as much as possible Reliability: should improve the reliability as much as possible Performance: should improve the user-perceived performance as much as possible

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Agenda „ „ „ „

Overview of Poratble Storage Technologies Techniques for High Performance Techniques for Low Power Conclusions

32

16

Conclusions „

In the animal world „

„

Survival of the fittest

In the memory world „

Survival of the fastest or cheapest Volatile

Non-volatile

Fastest

SRAM

FRAM?

Cheapest

DRAM

NAND Flash HDD

? 33

Conclusions „

From the history IBM 360/85

IBM 360/91

Clock Rate

80 ns

60 ns

Memory Speed

1040 ns

750 ns

Memory Interleaving

4 way

8 way

Additional Features

Cache Memory

Register Renaming, Out-of-order Execution, etc

But, IBM 360/85 faster on 8 of 11 programs! Source: David Patterson, et al., “A Case for Intelligent DRAM: IRAM”, Hot Chips VIII, August, 1996 34

17

The Ultimate Limit – Micro Drive

Fly By Night

2,000,000 Miles Per Hour Boeing 747

1/100” Flying Height

Source: http://www.hitachigst.com/

Source: Richard Lary, The New Storage Landscape: Forces shaping the storage economy, 2003.

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The Ultimate Limit – Flash Drive B/L Direction

200nm

W/L Direction

Source: K. Kim et al. IEDM Tech. Dig., 2002, pp. 919-922 36

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Announcement „

„ „

„

IWSSPS 2005: International Workshop on Software Support for Portable Storage Date: March 6, 2005 Place: San Francisco, USA (along with IEEE RTAS 2005 and Embedded System Conference 2005) Important Dates: „ „ „

Paper Submission: December 15th 2004 Notification of Acceptance: January 15th 2005 Camera-ready due: February 15th 2005

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„

Topics of interest include, but are not limited to: - File system for portable storage - Interaction between file system and portable storage - FTL (Flash Translation Layer) for Flash memory - Power management for HDD including microdrives - DRM (Digital Right Management) for portable storage - Distributed mobile storage - Software reliability for portable storage - Software fault tolerance techniques for portable storage

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