Solid State Drive

Amogha .B.4GM09EC006

INTRODUCTION

• The explosion of flash memory technology has dramatically increased storage capacity and decreased the cost of non-volatile semiconductor memory.

• SSDs do not contain any moving parts and depend on flash memory chips to store data.

• Flash memory chips store data in a large array of floating gate (MOS) transistors.

HISTORY

• FLASH MEMORY WAS INVENTED BY DR. FUJIO MASUOKA IN 1984.

• HE RECOMMENDED THE NAME ‘FLASH ‘ BY SEEING THE FLASH FROM CAMs.

OPERATION

OPERATION •Logic 1: erase mode.Logic 0: programming mode.

•Fowler-Nordheim tunneling is emission of electrons induced by an electrostatic field. The most common context is FE from a solid surface into vacuum solid or liquid surfaces, into air, a fluid, or any non-conducting or weakly conducting dielectric.

SERIAL ADVANCED TECHNOLOGY ATTACHMENT – SATA EX:HOST IINTERFACENAND FLASH SUPPORT 8 OR 16 BIT I/O BUS, HAVING INTERNEL 1KB BUS TRANSFER, SUPPORTS MULTIPLE NAND FLASH DEVICES, SUPPORTS FLOW THROUGH DMA DATA TRANSFERS RAM BUFFER IS MANAGED BY BML FOR FETCHING DATACHIPS-NAND MEMORY CHIPS

NAND FLASH CONTROLLER EEC – ERROR CORRECTION CODENAND USES BLOCK CODE (n,k) k- DATA BITShttp://www.quicklogic.com/assets/pdf/data_sheets/QL_NAND_Flash_Controller_PSB_DS_RevA.pdf

Software Layers SSD

• Buffer Management Layer- accept data and stores in buffer

• Flash Translation Layer- data placed into flash memory

• The GC overhead (i.e., the merge cost) is critical to the performance of an SSD & blocks user requests. Merge – victim pages replaced by free block.

Live Page Copying

•PAGE BUFFERS ARE USED BECAUSE PAGES WILL NOT EJECT TILL THE BUFFER IS FULL.•DATA CACHE IS USED MAINLY TO REDUCE THE TIME.

PAGE PLACEMENT IN SDD

• PA (PAGE AFFINITY) USES INTRA COPING.• CA (CHIP AFFINITY) USES CROSS PLANE .• NA (NON AFFINITY) USES CROSS CHIP.• TARGET PLANE SELECTION IN PA

CROSS-LAYER OPTIMIZATION

• TO ACHIVE PARRELLISM WITH LOW GC .• USING FAP (First Available Plane)-LRU.• BLOCK REPOSITIONING METHOD.

FAP (First Available Plane)-LRU.

• Recency and degree of parallelism• SELECTION OF VICTIM PAGE• P= BTPL( 1/ Nb)Nb represents the number of

pages per block and the table BTPL(i.e., Block-To-plane)

FAP-LRU AND LRU

BLOCK REPOSITIONING

• EFFECTIVENESS OF FRU-LRU DECREASES WITH LARGE SIZED DATA.

• PLANE1 PLANE 2 .• PLANE1 DEAD AFTER COPING TO PLANE2 SO

REDUCES TIME IN FUTURE MERGE.

PERFORMANCE EVALUATIONPARAMETERS value

SSD CAPACITY 80 GB

BUFFER CACHE/SEARCH WINDOW SIZE

20MB/5MB

#OF BUSES/PLANES PER CHIP

10/8

PAGE READ/WRITE 25us/200us

TRACES # OF PAGE READ/WRITE

WRITE RATIO (%)

AVERAGE READ /WRITE REQUEST SIZE

WIN 204180/188675

48 5.8/5.4

SQL 294918/293562

49.9 15.3/14

MSN 104513/67477

39 2.6/3.2

4VMs 478/323684

99.9 2.4/5.9

IOZ 19718/43218

69.3 21.1/84.2

PERFORMANCE RESULTS

WIN SQ

LM

SN4VM

sIO

Z0

1

2

3

4

5

6

7

8

PACANAPROPOSED

WIN SQ

LM

SN4VM

sIO

Z0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

WITH BLOCKWITHOUT BLOCKING

DEMAND FOR SSDS AND HDDS IN PORTABLE COMPUTERS

2005 2006 2007 2008 2009 2010 20110

50

100

150

200

250

SDDHDD

CHALLENGES

• LATENCY IS LOW, TIME REQUIRED TO LOCATE A FILE• SURVIVAL - IOPS IS GREAT BUT LIMITED WRITE

CYCLES THAN HDD• FTL - LATENCY SPIKES(TIME DELAY) AND LIMITED

DURABILITY.• FOR SDD GEOMETRY IS HIGHLY VIRTUALIZED

GEOMETRY OF HARD DISK• DATA IS ACCESSED BY MOVING HEAD IN AND OUT OF THE DISK•DAT STORED IN CONCENTRIC CIRCLES

ADVANTAGES

• HIGH START UP RATE-NO MOVING PARTS• DATA TRANSFER RATE IS HIGH 100-600 MB/S• NO NOISE• TO NEED OF TEMPERATURE COOLER• SHOCK RESISTIENT• WEIGHT & SIZE IS LESS Height is NOT standardized -

there are 7.5mm and 9mm SSDs • POWER CONSUMPTION IS LESS.

DISADVANTAGES

• STORAGE CAPACITY IS LESS 2TB IN 2011• SLOWER WRITE SPEEDS BECAUSE OF THE ERASE

BLOCKS ARE BECOMING LARGER AND LARGER.• For low capacity flash SSDs, low power consumption

and heat production when in active use. High capacity SSDs may have significant higher power requirements.

• COST IS HIGH.

APPLICATIONS

• CLOUD COMPUTING-ACCESS OVER INTERNET NEEDS SPEED• UNTIL 2009, SSDS WERE MAINLY USED IN THOSE ASPECTS OF

MISSION CRITICAL APPLICATIONS• FLASH MEMORY.• USB .• STORAGE DEVICES.• E-MAIL SERVICES IT NEEDS QUICK RESPONSE .• VIRTULIZATONS OF I/O CAN BE DONE.• DATA BASE & OLTP – ONLINE TRANSACTION PROCESS.

CONCLUSION

• SSDs utilize parallel architectures to improve their I/O throughput.

• The results show that there is no best policy due to the tradeoff between the degree of parallelism and the GC overhead.

• FTL- GC OVER HEAD LOW, BML DEGREE OF PARALLISM

• SIMULATION RESULTS IMPROVES RESPONSE TIME TO 79%

REFERENCES

• IEEETrans. Comput., vol. 60, no. 6, pp. 753–766, 2011 BY M. L. Chiao and D.W. Chang.

• H. Shim, B. Seo, J. Kim, and S. Maeng, “An adaptive partitioning scheme for DRAM-based cache in solid state drives,” in Proc. IEEE IN NOV 2010

• R. McDougall and J. Mauro, FileBench [Online]. Available: http:// www.solarisinternals.com/si/tools/filebench/

• http://www.intel.com/pressroom/.html• http://www.physorg.com/news/.html• http://www.storageview.com/.html

THANK YOU

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