microsoft powerpoint - prac2004
TRANSCRIPT
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Love/Hate Relationship between Flash Memory and Microdrive for Low-Power Portable Storage
2004. 09. 26Sang Lyul Min
Seoul National University&
Samsung Electronics
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Agenda
Overview of Portable Storage TechnologiesTechniques for High PerformanceTechniques for Low PowerConclusions
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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
Portable Storage
Flash Drive
Hitachi
Samsung
LexarMediaSanDisk
Toshiba
Micro Drive
IBM Hitachi
Seagate
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Cost Comparison
$299.88 (2004.8)
$259.88 (2004.8)
$399.95 (2004.8)
Source: http://www.hitachigst.com/hdd/technolo/overview/chart03.html
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NAND Flash Memory Basics
SpareData
…
SpareData
SpareData
SpareData
SpareData
…
SpareData
SpareData
SpareData
SpareData
…
SpareData
SpareData
SpareData
………
2j blocks
2i
pages
Read physical page (chip #, block #, page #)~ 25 us
Write physical page(chip #, block #, page #)~ 300 us
Erase block(chip#, block #)~ 2 ms
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FTL (Flash Translation Layer)Definition
Software layer that makes flash memory appear to the system likea disk drive
Challenges in FTLAsymmetry in read and write speedsNo overwrite is allowed without erasing
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Logical interface for a disk drive
Operations1. Identify drive(): returns N2. Read sectors(start sector #, # of sectors)3. Write sectors(start sector #, # of sectors)
512B 512B 512B…0 1 N -1
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Block level mapping
Logical blocks
…0 1 N -1
0
…
N / 256
……
256 sectors
Sectors
Logical blocks
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Block level mapping
Logical to physical block mapping
0
… …… …
… … …
1 L
Physical blocks
Logical blocks
… …
Visible (data blocks) Invisible
…
Block mapping table
(map block)
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Read procedure
Ex. read 3 sectors from 255
0
… …… …
Block mapping table
(map block)
… … …
1 L
Physical blocks
… …
…
Logical blocks
R R R
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Write procedure (Data block update)
Ex. write 3 sectors from 255
0
… …… …
Block mapping table
(map block)
… … …
1 L
… …
…
Write buffer blocks
… … …… …
1. Erase write buffer blocks for data
W W W
2. Write data pages3. Fill remaining data pagesStill, update of mapping information is needed
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Write procedure (Map block update)
Ex. write 3 sectors from 255
0
… …… …
Block mapping table
(map block)
… … …
1 L
… …
…
Write buffer blocks
……… …WWW
4. Erase write buffer blocks for map
W
5. Read-modify-write map page6. Fill remaining map pagesStill, somewhere we need to keep the addresses of new map and write buffer blocks (i.e., logging)
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Inside Hard Disk Drive
HostInterface
CPUcore SRAM/DRAM
System Bus
Platters
USB, PCMCIA, SATA
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ATA SCSI SERIAL
SAS3Gbps
Ultra320 SCSI
Ultra160 SCSI
Ultra2 SCSIUltra SCSISCSI-3SCSI-2SCSI-1
IEEE 1394a
ATA1 ATA2 U-ATA33U-ATA66USB 2.0
USB 1.1
S-ATA1
S-ATA2
IEEE 1394b
SAS6Gbps
S-ATA3
IEEE 1394b
IEEE 1394b
Transfer Rate (MB/s)
Host Interface Performance
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HDD Form Factor and Capacity
Source: http://www.hitachigst.com/hdd/technolo/overview/chart01.html
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HDD Internal Data Rate
Source: http://www.hitachigst.com/hdd/technolo/overview/chart16.html
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Inside Flash Drive
HostInterface
FlashInterface
CPUcore SRAM
USB, PCMCIA, SATA
System Bus
Flash Chips
Flash Bus
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Flash Chip Bandwidth
Write bandwidth = 2KB/300us = 6.7MB/s per chipRead bandwidth = 2KB/25us = 80MB/s per chipErase bandwidth = 128KB/2ms = 64MB/s per chip
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Flash
Flash bus bandwidth picture
Source: Terry Lee, Micron Technology, Inc, VTF (VIA Technology Forum) 2003
20~33Mb/s per Pin
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Agenda
Overview of Portable Storage TechnologiesTechniques for High PerformanceTechniques for Low PowerConclusions
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Techniques for High Performance Flash Drive
HostInterface
FlashInterface
CPUcore SRAM
USB, PCMCIA, etc
System Bus
Flash Chips
Flash BusHigh speed Flash bus
“Sleeping with the enemy”
Multiple logical chips in a single
packaging(multi-banking)
“Getting out of the way”
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Techniques for High Performance HDD
Source: http://www.hitachigst.com/hdd/technolo/overview/chart19.html
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Agenda
Overview of Mobile Storage TechnologiesTechniques for High PerformanceTechniques for Low PowerConclusions
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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, ArvindKrishnamurthy, 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 withreduced
power consumption and start-up time
HDD NAND Flash
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Why HDD+Flash Combo?
1. Power consumption aspects:In a laptop PC, HDD consumes
~10% (~2W) total power when disk platters are spinning~1% (~0.2W) total power when disk platters are idle
2. Cost aspects:128MB Flash write buffer
< $8 in 2006< $4 in 2008
3. Reliability aspects:4. Performance aspects:
Source: Clark Nicholson, “Improved Disk Drive Power Consumption Using Solid State Non-Volatile Memory”, WinHEC2004.
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HDD+Flash Combo Block Diagram
HostInterface
FlashInterface
CPUcore SRAM
SATAFlash Chip
Flash Bus
System Bus
Platters
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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 @ .18WTon = 18s @ 2.5W
Ton = spin up time (5s) + Flash buffer flush time (13s)Flash buffer size = 128MBTransfer rate = 10MB/s
Source: Clark Nicholson, “Improved Disk Drive Power Consumption Using Solid State Non-Volatile Memory”, WinHEC2004.
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Key Considerations
1. Correctness: should preserve the semantics of HDD2. Fault tolerance and graceful degradation: should operate
correctly despite partial/total failure in flash memory3. Power efficiency: should reduce the power consumption
as much as possible4. Reliability: should improve the reliability as much as
possible5. Performance: should improve the user-perceived
performance as much as possible
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Agenda
Overview of Poratble Storage TechnologiesTechniques for High PerformanceTechniques for Low PowerConclusions
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Conclusions
In the animal worldSurvival of the fittest
In the memory worldSurvival of the fastest or cheapest
NAND FlashHDD
DRAMCheapestFRAM?SRAMFastest
Non-volatileVolatile ?
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Conclusions
From the history
Register Renaming, Out-of-order Execution,
etcCache MemoryAdditional Features
8 way4 wayMemory Interleaving
750 ns1040 nsMemory Speed
60 ns80 nsClock Rate
IBM 360/91IBM 360/85
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
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The Ultimate Limit – Micro Drive
FlyBy
NightBoeing 747
2,000,000 Miles Per Hour
1/100” Flying Height
Source: Richard Lary, The New Storage Landscape: Forces shaping the storage economy, 2003.
Source: http://www.hitachigst.com/
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The Ultimate Limit – Flash Drive
B/L Direction
W/L Direction
Source: K. Kim et al. IEDM Tech. Dig., 2002, pp. 919-922
200nm
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Announcement
IWSSPS 2005: International Workshop on Software Support for Portable StorageDate: March 6, 2005Place: San Francisco, USA (along with IEEE RTAS 2005 and Embedded System Conference 2005)Important Dates:
Paper Submission: December 15th 2004Notification of Acceptance: January 15th 2005Camera-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