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# MEMS-based storage system

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• Disk 의 용량은 매년 60% 증가 , Access time 도 매년 7% 씩 증가하고는 있지만 , disk 의 물리적인 특성 때문에 gab 은 더더욱 벌어지고 있음 .
• 처음에는 디스크와 같은 rotating device, 고정 미디어 / 동작 헤드 등의 여러가지의 디자인들이 제시되었으나 , 시간 / 공간 효율성 면에서 고려하여 이 모델이 결정되었음 .
• So, to understand what’s going on, let’s consider a simple seek.
• So what is the seek time? What this graph is showing is the seek time in milliseconds as a function of displacement. Think of it as seek time as a function of distance. What I’m showing is the seek time from the center of the square (click) to the outer reaches (click). Starting at the center, first there is the constant overhead of the settling time, about 0.2 ms, and then seek time increases to a maximum of around 0.64 ms at the outer edges. This graph is showing seek time in only one dimension, X. One of the interesting things about this device is that seeks are in two dimensions. What happens if we look at that?
• S piring 의 복원력 때문에 외부 영역이 내부 영역에 비해 access time 이 약간 더 크다 .
• ### MEMS-based storage system

1. 1. MEMS-based Storage System Kim Tae Seok (2004.7.20.)
2. 2. MEMS in terms of research topic <ul><li>Research Trend in OSLAB </li></ul>MEMS-based storage system topic is in the infancy !!! 2004 time Web server/cache Multimedia system Flash memory Low power system Ubiquitous Computing MEMS-based storage?
3. 3. Contents <ul><li>What is MEMS(MEMS-based storage)? </li></ul><ul><li>Why MEMS-based storage? </li></ul><ul><li>MEMS-based storage structure </li></ul><ul><li>OS view of MEMS-based storage </li></ul><ul><li>The future for MEMS-based storage </li></ul>
4. 4. W hat is MEMS(MEMS-based storage)?
5. 5. The need of new storage technology The RAM-to-disk performance gab - 6 orders of magnitude in 2000 - widen by 50% per year Disk RAM CPU time speed gab cache memory gab ?
6. 6. Alternatives to Disk <ul><li>Solid state storage </li></ul><ul><ul><li>Flash memory </li></ul></ul><ul><ul><li>Ferro-electric (FeRAM) </li></ul></ul><ul><ul><li>Magnetic RAM (MRAM) </li></ul></ul><ul><ul><li>Polymer </li></ul></ul><ul><ul><li>Chalcogenic/Ovonicmaterials </li></ul></ul><ul><ul><li>Organics (protein, DNA) </li></ul></ul><ul><li>Non-rotating magnetic media </li></ul><ul><ul><li>MEMS </li></ul></ul><ul><li>Small-format arrays (multiple disks in one package) </li></ul>
7. 7. What is MEMS? <ul><li>M icro E lectro M echanical S ystem </li></ul><ul><ul><li>the integration of mechanical elements, sensors, actuators, and electronics on a common silicon substrate through microfabrication technology. </li></ul></ul><ul><ul><ul><li>electronics parts : integrated circuit (IC) process (e.g., CMOS) </li></ul></ul></ul><ul><ul><ul><li>micromechanical parts : micromachining processes </li></ul></ul></ul><ul><li>MEMS promises to make possible the realization of complete systems-on-a-chip . </li></ul><ul><ul><li>Enable co-location of nonvolatile storage, RAM, network module and processing on same physical chip </li></ul></ul><ul><ul><li>augments the decision-making capability with &quot;eyes&quot; and &quot;arms&quot;, to allow microsystems to sense and control the environment. </li></ul></ul>
8. 8. Applications of MEMS <ul><li>Ubiquitous use in everyday world !!! </li></ul><ul><ul><li>Ongoing research </li></ul></ul><ul><ul><ul><li>Sensors/Actuators </li></ul></ul></ul><ul><ul><ul><ul><li>accelerometers </li></ul></ul></ul></ul><ul><ul><ul><ul><li>micromirror arrays for LCD projectors </li></ul></ul></ul></ul><ul><ul><ul><ul><li>heads for inkjet printers </li></ul></ul></ul></ul><ul><ul><ul><ul><li>optical switches </li></ul></ul></ul></ul><ul><ul><ul><ul><li>… </li></ul></ul></ul></ul><ul><ul><li>MEMS-based storage </li></ul></ul>
9. 9. W hy use MEMS-based storage?
10. 10. Why Use MEMS-based Storage? <ul><li>Cost </li></ul><ul><ul><li>10X cheaper than RAM </li></ul></ul><ul><ul><li>Lower cost-entry point than disk </li></ul></ul><ul><ul><ul><li>\$10-\$30 for ~10 Gbytes </li></ul></ul></ul>0.01 GB 0.1 GB 1 GB 10 GB 100 GB \$1 \$10 \$100 \$1000 CACHE RAM DRAM HARD DISK Entry Cost MEMS Capacity @ Entry Cost
11. 11. Why Use MEMS-based Storage? <ul><li>Volume </li></ul>10 GByte/cm 2 = 65 GB/in 2 density (100x CD-ROM) 30 nm x 30 nm bit size 100,000 Occupied volume [cm 3 ] 0.1 1 10 100 1000 10,000 0.1 10 100 1000 10,000 3.5” Disk Drive Flash memory, 0.4 µm 2 cell Chip-sized data storage @ 10 GByte/cm 2 1 Storage Capacity [GByte]
12. 12. Why Use MEMS-based Storage? <ul><li>Data latency </li></ul>No rotation delay 10x faster access time than today’s disk drive Worst-Case Access Time (Rotational Latency) Cost \$ / GB \$1 / GB \$3 / GB \$10 / GB \$30 / GB \$100 / GB 10ns 1µs 100µs 10ms DRAM HARD DISK Prediction 2008 \$300 / GB EEPROM (Flash) MEMS
13. 13. Why Use MEMS-based Storage? <ul><li>Storage 10 Gbytes of data in the size of a penny </li></ul><ul><li>Deliver 100 MB – 1 GB/sec bandwidth </li></ul><ul><li>Deliver access times 10X faster than today’s drives </li></ul><ul><li>Consume ~100X less power than low-power disk drives </li></ul><ul><li>Cost less than \$10 </li></ul><ul><li>Integrate storage, RAM, and processing on the same die </li></ul>
14. 14. Why Not EEPROM? <ul><li>We have computers on a chip now (Embedded computers) </li></ul><ul><ul><li>Currently nonvolatile memory is EEPROM (FLASH memory) </li></ul></ul><ul><li>EEPROM Feature (size and cost) </li></ul><ul><ul><li>Taking EEPROM prices as \$0.27/MB --> \$2,700 / 10GB </li></ul></ul><ul><ul><li>For MEMS-based Storage in 2009 we predict cost ~\$25 / 10GB </li></ul></ul><ul><ul><ul><li>> 100X better than EEPROM </li></ul></ul></ul>\$0.27 \$0.53 \$1 \$1.5 \$2 \$4 EEPROM cost(\$/MB) 240 120 64 44 32 16 density(MB/cm 2 ) 0.04 0.08 0.15 0.22 0.3 0.6 NOR Cell Area(um 2 ) 2009 2006 2003 2001 1999 1997
15. 15. MEMS-based storage is available now? <ul><li>MEMS-based storage devices are still several years away from commercialization </li></ul><ul><ul><li>Design details are not revealed </li></ul></ul><ul><li>Many designs are possible </li></ul><ul><ul><li>While design details for MEMS are differ, most use a similar media sled design </li></ul></ul><ul><ul><ul><li>Ongoing device development company </li></ul></ul></ul><ul><ul><ul><ul><li>IBM(Millipede), Hewlett-Packard, Kionix, Nanochip </li></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>http:// www.zurich.ibm.com/st/storage/millipede.html </li></ul></ul></ul></ul></ul><ul><ul><ul><li>Ongoing software research group </li></ul></ul></ul><ul><ul><ul><ul><li>Computer Systems LAB. of Carnegie Mellon University </li></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>http://www.lcs.ece.cmu.edu/research/MEMS </li></ul></ul></ul></ul></ul><ul><ul><li>Feedback loop with MEMS device group </li></ul></ul><ul><ul><ul><li>Design parameter (e.g., the number of tips) </li></ul></ul></ul>
16. 16. Design parameter Example <ul><li>size : 1-1.5 cm 2 </li></ul><ul><li>capacity : 2-10GB </li></ul><ul><li>power : 1-3W (during access) </li></ul><ul><li>avg. access time : 1-3ms (random) </li></ul><ul><li>bandwidth: 10-100MB/sec </li></ul><ul><li>many tradeoffs </li></ul><ul><ul><li># of active tips, multiple sleds, etc </li></ul></ul><ul><ul><li>capacity vs. latency vs. power vs. bandwidth </li></ul></ul>
17. 17. MEMS-based storage structure
18. 18. MEMS-based Storage <ul><li>On-chip Magnetic Storage - using MEMS for media positioning </li></ul>Read/Write tips Magnetic Media Actuators
19. 19. MEMS-based Storage Read/write tips Media side view Bits stored underneath each tip
20. 20. MEMS-based Storage Media Sled X Y
21. 21. MEMS-based Storage Springs Springs Springs Springs X Y
22. 22. MEMS-based Storage Anchors attach the springs to the chip. Anchor Anchor Anchor Anchor X Y
23. 23. MEMS-based Storage Sled is free to move X Y
24. 24. MEMS-based Storage Sled is free to move X Y
25. 25. MEMS-based Storage Springs pull sled toward center X Y
26. 26. MEMS-based Storage Springs pull sled toward center X Y
27. 27. MEMS-based Storage Actuators pull sled in both dimensions Actuator Actuator Actuator Actuator X Y
28. 28. MEMS-based Storage Actuators pull sled in both dimensions X Y
29. 29. MEMS-based Storage Actuators pull sled in both dimensions X Y
30. 30. MEMS-based Storage Actuators pull sled in both dimensions X Y
31. 31. MEMS-based Storage Actuators pull sled in both dimensions X Y
32. 32. MEMS-based Storage Probe tips are fixed Probe tip Probe tip X Y
33. 33. MEMS-based Storage Probe tips are fixed X Y
34. 34. MEMS-based Storage X Y Sled only moves over the area of a single square One probe tip per square Each tip accesses data at the same relative position
35. 35. Managing MEMS-based Storage <ul><li>MEMS Data Layout </li></ul>Sector is 8 data bytes + ECC + servo Media area divided into “ regions” 2500 2500 Data stored in “sectors” of ~100 bits
36. 36. Read-modify-write example 1 2 3 2500 …
37. 45. Fast Read-Modify-Write <ul><li>Disks must wait an entire disk rotation to perform a read-modify-write </li></ul><ul><ul><li>MEMS devices can quickly turn around and write (or rewrite a sector) </li></ul></ul><ul><ul><li>Example: Read-modify-write of 8 sectors (4KBytes) in msecs </li></ul></ul><ul><ul><ul><li>Atlas 10K MEMS </li></ul></ul></ul><ul><ul><li>Read 0.14 0.13 </li></ul></ul><ul><ul><li>Reposition 5.98 0.07 </li></ul></ul><ul><ul><li>Write 0.14 0.13 </li></ul></ul><ul><ul><li>Total 6.26 0.33 </li></ul></ul>
38. 46. X-dimension Settling Time <ul><li>Consider a simple seek </li></ul>... ... ... ... Sweep area of one probe tip Why do we only care about the X dimension? Oscillations in X Oscillations in Y
39. 47. X-dimension Settling Time Why do we only care about the X dimension? Oscillations in X lead to off-track interference! In Y, the oscillations appear as slight variations in velocity, which can be tolerated. Sled is moving in Y
40. 48. Seek Time from Center 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 -1000 -500 0 500 1000 Seek time (ms) X displacement (bits)
41. 49. OS view of MEMS-based storage
42. 50. OS view of MEMS-based storage <ul><li>High-level MEMS characteristics: </li></ul><ul><ul><li>Long positioning times </li></ul></ul><ul><ul><li>High streaming rate </li></ul></ul><ul><li>Logical block interface works well </li></ul><ul><ul><li>Opportunities for device optimization, but convoluted tricks not necessary </li></ul></ul>
43. 51. Disk scheduling
44. 52. MEMS scheduling Curves saturate in same order, relative position
45. 53. Disk vs. MEMS-based storage <ul><li>H ow to schedule requests? </li></ul>Disk One-dimension problem MEMS Two-dimensions problem in out probe tip
46. 54. Data layout <ul><li>Basically as for disks </li></ul><ul><ul><li>Sequential access >>> not sequential </li></ul></ul><ul><ul><li>Local access > not local </li></ul></ul><ul><li>Some interesting differences </li></ul><ul><ul><li>File size vs. physical location </li></ul></ul>
47. 55. Small requests 0.42 ms/move in this subregion 0.37 ms/move in this subregion
48. 56. Large requests: 256KB <ul><li>Transfer time dominates positioning time </li></ul>Short seek Long seek 0 MAX
49. 57. Bipartite layout Metadata or small objects Large/streaming objects
50. 58. Failure Management <ul><li>MEMS devices will have internal failures </li></ul><ul><ul><li>Tips will break during fabrication/assembly … and during use </li></ul></ul><ul><li>With multiple tips, data and ECC can be striped across the tips </li></ul><ul><ul><li>ECC can be both horizontal and vertical </li></ul></ul><ul><ul><li>On tip or tip-media failure, ECC prevents data loss </li></ul></ul><ul><ul><li>Could then use spares to regain original level of reliability </li></ul></ul>
51. 59. Failure Management <ul><li>MEMS devices will have internal failures </li></ul><ul><ul><li>Tips will break during fabrication/assembly … and during use </li></ul></ul><ul><ul><li>Media can wear </li></ul></ul>Probe Tip Spare Tip Spare Tip
52. 60. Failure Management <ul><li>MEMS devices will have internal failures </li></ul><ul><ul><li>Tips will break during fabrication/assembly … and during use </li></ul></ul><ul><ul><li>Media can wear </li></ul></ul>Probe Tip Spare Tip Spare Tip
53. 61. MEMS in Computer Systems <ul><li>MEMS-based storage device simulator </li></ul><ul><ul><li>Uses first-order mechanics </li></ul></ul><ul><li>Integrated into DiskSim </li></ul><ul><ul><li>Models events, busses, cache </li></ul></ul><ul><ul><li>Compare against simulated disks </li></ul></ul><ul><li>SimOS-Alpha </li></ul><ul><ul><li>Full machine simulator with DiskSim as storage subsystem </li></ul></ul>
54. 62. Random Workload - 15X Speedup 10,000 small random requests, 67% reads, exponentially sized with mean 4KB. MEMS has small positioning variability
55. 63. MEMS-based Storage as Disk Cache File System Disk MEMS Cache HP Cello trace has 8 disks 10.4GB total capacity 1999 Disk (Quantum Atlas 10K) 9 GB Baseline MEMS 3 GB
56. 64. Disk Cache Configuration File System Disk MEMS Cache Disk MEMS Cache Disk MEMS Cache Disk MEMS Cache
57. 65. MEMS-based Storage As a Disk Cache
58. 66. File System-managed Layout <ul><li>File system could allocate data directly </li></ul>MEMS Disk File system <ul><li>Metadata </li></ul><ul><li>Small files </li></ul><ul><li>Paging </li></ul><ul><li>Large, streaming files </li></ul>
59. 67. Low-power Disk Drives <ul><li>IBM Travelstar 8GS </li></ul>Perf Idle Fast Idle Low power Idle Standby Active Time (s) Power (W) 0 1 2 3 0 5 10 Command stream ends 40 ms 2 s 400 ms
60. 68. MEMS-based Storage <ul><li>Lower operating power </li></ul><ul><ul><li>100 mW for sled positioning </li></ul></ul><ul><ul><li>1 mW per active tip </li></ul></ul><ul><ul><li>For 1000 active tips, total power is 1.1 watt </li></ul></ul><ul><ul><li>50 mW standby mode </li></ul></ul>0.5 ms <ul><li>Fast transition from standby </li></ul>Active Time (s) Power (W) 0 1 0 5 10 Standby (not to scale)
61. 69. PostMark 3111 58
62. 70. PostMark Performance Idle Active Active
63. 71. Conclusions
64. 72. Future of MEMS-based Storage <ul><li>Perfect for portable devices </li></ul><ul><ul><li>Size, capacity, power </li></ul></ul>
65. 73. System-on-a-Chip <ul><li>Filling memory gap </li></ul><ul><li>Operating system support </li></ul><ul><ul><li>Scheduling </li></ul></ul><ul><ul><li>Data layout </li></ul></ul><ul><ul><li>Fault management </li></ul></ul><ul><li>New applications </li></ul><ul><ul><li>PDA, digital music, video, archival storage </li></ul></ul>2 cm 2 cm
66. 74. MEMS-based Storage Is On the Way <ul><li>Interesting new storage technology </li></ul><ul><ul><li>Gigabytes of non-volatile data in a single IC </li></ul></ul><ul><ul><li>Sub-millisecond average access time </li></ul></ul><ul><ul><li>Low power </li></ul></ul><ul><li>Can fill various roles </li></ul><ul><ul><li>Augment memory hierarchy </li></ul></ul><ul><ul><li>Portable devices </li></ul></ul><ul><ul><li>Active storage devices </li></ul></ul>
67. 75. R esearch topic <ul><li>What applications are beneficial? </li></ul><ul><ul><li>Developing n ew applications </li></ul></ul><ul><li>W here/how to use it in a system? </li></ul><ul><ul><li>S ystem architecture </li></ul></ul><ul><li>H ow can maximize it’s performance as a storage? </li></ul><ul><ul><li>U sing parallelism effectively </li></ul></ul><ul><ul><li>… </li></ul></ul>
68. 76. Conclusions <ul><li>MEMS-based storage </li></ul><ul><ul><li>It is an exciting new technology :) </li></ul></ul><ul><ul><ul><li>Large capacity, l ow cost, low volume, low power, … </li></ul></ul></ul><ul><ul><li>B lock device (e.g., disk) background in OSLAB may be helpful. :) </li></ul></ul><ul><ul><ul><li>I/O scheduling, data layout … </li></ul></ul></ul><ul><ul><li>B ut, it is not available now … :( </li></ul></ul>
69. 77. R eference <ul><li>[1] Schlosser, S., Griffin, J., Nagle, D., Ganger, G., Filling the Memory Access Gap: A Case for On-Chip Magnetic Storage. Technical Report CMU-CS-99-174, Carnegie Mellon University School of Computer Science, November 1999. </li></ul><ul><li>[2] Schlosser, S., Griffin, J., Nagle, D., Ganger, G., Designing Computer Systems with MEMS-based Storage. In ASPLOS 2000, November 13-15, 2000. </li></ul><ul><li>[3] L. Richard Carley, Gregory R. Ganger, and David F. Nagle, MEMS-Based Integrated-Circuit Mass-Storage Systems. in COMMUNICATIONS OF THE ACM November 2000, Vol.43, No.11. </li></ul><ul><li>[4] Griffin, J., Schlosser, S., Ganger, G., Nagle, D., Operating Systems Management of MEMS-based Storage Devices. In OSDI 2000, October 23-25, 2000. </li></ul><ul><li>[5] Griffin, J., Schlosser, S., Ganger, G., Nagle, D., Modeling and Performance of MEMS-Based Storage Devices. In Proceedings of SIGMETRICS 2000, June 18-21, 2000. Published as Performance Evaluation Review 28(1):56-65, June 2000. </li></ul>
70. 78. R eference <ul><li>[6] Tara M. Madhyastha, Katherine Pu Yang, Physical Modeling of Probe-Based Storage. In Proceedings of the Eighteenth IEEE Symposium on Mass Storage Systems (April 2001). </li></ul><ul><li>[7] Z.N.J. Peterson, S.A. Brandt and D.D.E. Long. Data Placement Based on the Seek Time Analysis of a MEMS-based Storage Device. A Work in Progress (WIP) at: the Conference on File and Storage Technologies (FAST), USENIX, 2002. </li></ul><ul><li>[8] Pu Yang. Modeling Probe-based Storage Devices. Tehcnical report. Department of Computer Science, University of California Santa Cruz, June 2000. Master's thesis. </li></ul><ul><li>[9] B. Hong, Exploring the Usage of MEMS-based Strorage as Metadata Storage and Disk Cache in Storage Hierarchy. Department of Computer Science, University of California Santa Cruz. 2003 </li></ul><ul><li>[10] Steven W. Schlosser, Jiri Schindler, Anastassia Ailamaki, and Gregory R. Ganger, Exposing and Exploiting Internal Parallelism in MEMS-based Storage. Carnegie Mellon University Technical Report CMU-CS-03-125, March 2003. </li></ul>
71. 79. R eference <ul><li>[11] M. Uysal, A. Merchant, and G. Alvarez, Using MEMS-based stroage in disk arrays. Proc. of 2nd USENIX Conference on File and Storage Technologies, April 2003 </li></ul><ul><li>[12] Hailing Yu, Divyakant Agrawal, and Amr El Abbadi, Towards Optimal I/O Scheduling for MEMS-Based Storage. 20 th IEEE/11 th NASA Goddard Conference on Mass Storage Systems and Technologies (MSS'03) April 07 - 10, 2003 San Diego, California </li></ul><ul><li>[13] H. Yu, D. Agrawal, and A. E. Abbadi, Tabular Placement of Relational Data on MEMS-based Storage Devices. In proceedings of the 29th Conference on Very Large Databases(VLDB), 680-693. September 2003 </li></ul><ul><li>[14] MEMS-based Storage Systems (including slides from OSDI, Sigmetrics and ASPLOS) ppt. Carnegie Mellon University School of Computer Science </li></ul>