Solid State Drives: A Closer Look

SUMMARY

Solid State Drives: A Closer Look provides a detailed overview of the technology, architecture and reliability of SSDs as well as techniques for improving the performance and endurance of SSDs. The report also describes measures to increase the endurance of NAND flash on the device level such as in the ultra high endurance server-grade NAND flash from Samsung.

Currently, there is a wide range of SSD performance and quality from various suppliers. An overview of SSD-related patents reveals which companies may have a long-term competitive advantage in this nascent market.

The report also includes a comparison of SSDs in the enterprise, low cost mobile notebook PC, notebook PC and desktop PC segments as well as a workload analysis of applications in the enterprise space. Detailed revenue, unit and price forecasts are provided for all segments.

TABLE OF CONTENTS

CONTENTS III

LIST OF FIGURES VI

LIST OF TABLES IX

EXECUTIVE SUMMARY 1

INTRODUCTION 3

NAND FLASH MEMORY OVERVIEW 4

• NAND Flash 4
  • Concept 4
  • Technology Evolution 6
  • NAND Flash Architecture 9
  • NAND Flash Density Trend 11
  • Page Size Trend 13
  • Block Size Trend 14
  • Read Time 14
  • Program Time 16
  • Endurance 17
  • Retention 17

SOLID STATE DRIVES 19

• What is a solid state drive? 19
• The Memory Hierarchy 19
• SSD Overview 22
• SSD Architecture 25
• Controller 27
  • Flash Translation Layer 28
  • Mapping Schemes 30
  • Bad Block Management 33
  • Wear-leveling 33
  • Garbage Collection 35
  • Error Correction 36
  • Interleaving 37
  • Power Loss Protection 37
• Techniques for Improving SSD Performance/Endurance 38
  • Caching 38
  • Flash File System Optimization 38
  • Parallelism 39
  • Flash Bus Width 40
  • Over-provisioning 40
  • Improved NAND Flash Memory 41
  • Re-mapping of Drive Block 43
• Alternative SSD Architectures 45
  • Chameleon 45
  • Hybrid SSD 46
  • HyperLink NAND 49
• SSD Reliability 52
  • Mean Time Between Failure (MTBF) 52
  • Endurance 52
  • Program Disturb 55
  • Read Disturb 55
  • Data Retention 56
  • Bit Error Rate 57
  • SMART 61

SSD VS. HDD 62

• Enterprise Applications 62
• PC Applications 66
• Low Cost Mobile PC Applications 70
• Price / GB 73

SSD LANDSCAPE 74

• Chronology 74
• Vendor Landscape 75
• Standards 76
  • IDEMA 77
  • JEDEC 77
  • Non-Volatile Memory Host Controller Interface Specification (NVMHCI) 77
  • SNIA SSD Initiative 77
  • SSD Alliance 77
  • Technical Committee T13 AT Attachment 78
• Patent Overview 79
• Seagate vs. STEC 81

COMPUTING MARKET AND APPLICATIONS 83

• Enterprise Market 83
• Transaction Processing 84
• Video Server 84
• High Performance Computing 86
• Internet/Network Server 86
• Application Workload Characteristics 86
• Server-attached vs. Storage-attached SSDs 88
• Enterprise SSD Forecast 88
• Low Cost Mobile PC Market 99
• Notebook PC Market 106
• Desktop PC Market 113
• Computing SSD Market 117
• **REFERENCES CXIX
• **ABOUT THE AUTHOR CXXI

ABOUT FORWARD INSIGHTS CXXII

• Services cxxii
• Contact cxxii

List of Figures

• Figure 1. NAND Flash Cell Programming 4
• Figure 2. Multi-level Storage in NAND Flash 4
• Figure 3. NAND Flash Cell Reading 5
• Figure 4. NAND Flash Cell Erase 5
• Figure 5. NAND Cell String 6
• Figure 6. NAND Cell String 6
• Figure 7. NAND Flash Technology Evolution 7
• Figure 8. NAND Flash Memory Gap Fill 8
• Figure 9. Electrons Stored on the Floating Gate 8
• Figure 10. Samsung 32Gb CTF Memory 9
• Figure 11. NAND Flash Memory Architecture 10
• Figure 12. 8Gb NAND Flash Memory Organization 11
• Figure 13. NAND Flash Memory Density Trend 12
• Figure 14. NAND Flash Memory Chip Size Trend 13
• Figure 15. NAND Flash Page Size Trend 13
• Figure 16. NAND Flash Block Size Trend 14
• Figure 17. NAND Flash Random Access Time 15
• Figure 18. NAND Flash Read Performance Trend 15
• Figure 19. NAND Flash Program Time 16
• Figure 20. NAND Flash Write Performance Trend 16
• Figure 21. NAND Flash Endurance Trend 17
• Figure 22. NAND Flash Endurance Trend at 70nm Technology 18
• Figure 23. NAND Flash Endurance Trend at 3xnm Technology 18
• Figure 24. Memory Hierarchy 20
• Figure 25. NAND Flash vs. DRAM Process Technology 21
• Figure 26. Major Components of SSD and HDD 22
• Figure 27. 128GB MLC SSD vs. 128GB SLC SSD Bill of Materials 23
• Figure 28. NAND Flash as a % of Bill of Material 24
• Figure 29. SSD Architecture 25
• Figure 30. Two-channel, Four-way Interleaving 26
• Figure 31. Software Architecture 26
• Figure 32. SSD Controller Functional Block Diagram 27
• Figure 33. HDD vs. SSD Address Mapping 29
• Figure 34. Flash Translation Layer 29
• Figure 35. Page Mapping 31
• Figure 36. Block Mapping 32
• Figure 37. Hybrid Mapping 33
• Figure 38. Wear-leveling 35
• Figure 39. Garbage Collection 36
• Figure 40. SSD Operating Current 39
• Figure 41. MTron PATA SSD Functional Block Diagram 40
• Figure 42. High Speed NAND 42
• Figure 43. Improving Endurance through Reduced Vt Margins 43
• Figure 44. Chameleon SSD Architecture 45
• Figure 45. Chameleon SSD Performance 45
• Figure 46. Effect of Block-level and Page-level Write Buffer 46
• Figure 47. Hybrid SSD Concept 46
• Figure 48. Data/Control Flows in Hybrid SSD 47
• Figure 49. SSD Workload Profile 48
• Figure 50. Circular Log Space in SLC NAND flash 48
• Figure 51. Hybrid SSD Endurance 49
• Figure 52. HyperLink NAND SSD vs. Conventional SSD Architecture 50
• Figure 53. Minimum SSD Capacity for 5 Year Product Life 54
• Figure 54. Program Disturb 55
• Figure 55. Read Disturb 56
• Figure 56. Flash Error Rate Surface 57
• Figure 57. SSD vs. HDD Bit Error Rates 59
• Figure 58. ECC Selection 61
• Figure 59. SSD vs. HDD Random IOPS 63
• Figure 60. SSDs vs. HDDs in the Enterprise - Performance Characteristics 65
• Figure 61. Enterprise SSD vs. HDD Average Capacity 65
• Figure 62. SSDs vs. HDDs in PCs - Performance Characteristics 67
• Figure 63. SSD Performance Trend 68
• Figure 64. Notebook PC SSD vs. HDD Average Capacity 69
• Figure 65. Desktop SSD vs. HDD Average Capacity 69
• Figure 66. SSDs vs. HDDs in Low Cost Mobile PCs - Performance Characteristics 71
• Figure 67. LC Mobile PC SSD vs. HDD Average Capacity 72
• Figure 68. SSD vs. HDD Price Curve 73
• Figure 69. HDD and SSD Landscape 76
• Figure 70. SSD Patents by Type 79
• Figure 71. SSD-related Patents by Company 80
• Figure 72. Applications Write/Read Workload 87
• Figure 73. Applications Sequential/Random Workload 87
• Figure 74. Total Enterprise SSD Units Forecast 89
• Figure 75. Total Enterprise SSD Revenue Forecast 89
• Figure 76. Enterprise Storage Drive Units Forecast 90
• Figure 77. Enterprise Storage HDD Unit Forecast 91
• Figure 78. Enterprise Storage SSD Unit Forecast 92
• Figure 79. Enterprise Storage SSD GB Forecast 92
• Figure 80. Enterprise Storage SSD GB / Unit Forecast 93
• Figure 81. Enterprise Storage SSD $ / GB Forecast 93
• Figure 82. Enterprise Storage SSD Revenue Forecast 94
• Figure 83. Enterprise Server Units Forecast 95
• Figure 84. Host Server-attached SSD Unit Forecast 96
• Figure 85. Host Server-attached SSD GB Forecast 96
• Figure 86. Host Server-attached SSD GB / Unit Forecast 97
• Figure 87. Host Server-attached SSD $ / GB Forecast 97
• Figure 88. Host Server-attached SSD Revenue Forecast 98
• Figure 89. Low Cost Mobile PC Unit Forecast 99
• Figure 90. Endurance vs. SSD Capacity 100
• Figure 91. Low Cost Mobile PC SSD Unit Forecast 101
• Figure 92. Low Cost Mobile PC SSD GB Forecast 105
• Figure 93. Low Cost Mobile PC SSD Revenue Forecast 105
• Figure 94. Notebook PC Unit Forecast 106
• Figure 95. Notebook PC SSD Unit Forecast 107
• Figure 96. Notebook PC SSD GB Forecast 112
• Figure 97. Notebook PC SSD Revenue Forecast 112
• Figure 98. Desktop PC Unit Forecast 113
• Figure 99. Desktop PC SSD Unit Forecast 114
• Figure 100. Desktop PC SSD GB Forecast 116
• Figure 101. Desktop PC SSD Revenue Forecast 116
• Figure 102. Computing SSD Unit Forecast 117
• Figure 103. Computing GB Forecast 117
• Figure 104. Computing SSD Revenue Forecast 118

List of Tables

• Table 1. SSD Bill of Materials 23
• Table 2. ECC Trend 37
• Table 3. HLNAND SSD vs. Conventional SSD 51
• Table 4. SSD Capacity as a Function of Writes / Day 54
• Table 5. Enterprise Class SSD vs. HDD 64
• Table 6. PC-Class SSD vs. HDD 66
• Table 7. Interface Transfer Speeds 68
• Table 8. Interface Transfer Speeds 68
• Table 9. Low Cost Mobile PC SSD vs. HDD 70
• Table 10. SSD Chronology 74
• Table 11. Seagate's Patent Claims against STEC 81
• Table 12. Enterprise SSD vs. HDD Key Metrics 83
• Table 13. Video-on-Demand SSD TAM 85
• Table 14. Enterprise HDD:SSD Replacement Ratio 91
• Table 15. SSD NAND Flash Technology under Four Scenarios 100
• Table 16. LC Mobile PC SSD Capacity Unit Mix Forecast 102
• Table 17. LC Mobile PC SSD Capacity GB Mix Forecast 103
• Table 18. LC Mobile PC SLC SSD Price Forecast 103
• Table 19. LC Mobile PC MLC SSD Price Forecast 104
• Table 20. LC Mobile PC 3-bit per cell SSD Price Forecast 104
• Table 21. Notebook PC SLC SSD Capacity Unit Mix Forecast 108
• Table 22. Notebook PC SLC SSD Capacity GB Mix Forecast 109
• Table 23. PC SLC SSD Price Forecast 109
• Table 24. PC MLC SSD Price Forecast 110
• Table 25. PC SLC/3-bit per cell SSD Price Forecast 111
• Table 26. Desktop PC SSD Capacity Unit Mix Forecast 114
• Table 27. Desktop PC SSD Capacity GB Mix Forecast 115