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MEMS Based Mass Storage Systems. What is MEMS?. (M)icro(E)lectric(M)echanical(S)ystems Consist of mech µ(structures, sensors, actuators), electronics, integrated onto same chip Transducer = Sensor / Actuator Smart sensors Cheap Examples. Fender?.
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What is MEMS? • (M)icro(E)lectric(M)echanical(S)ystems • Consist of mech µ(structures, sensors, actuators), electronics, integrated onto same chip • Transducer = Sensor / Actuator • Smart sensors • Cheap • Examples
Fender? • The world's smallest guitar is 10 micrometers long – • Made by Cornell University researchers from crystalline silicon
Why use MEMS? Capacity @ Entry Cost • Cost • Examples 100 GB HARD DISK MEMS 10 GB 1 GB 0.1 GB DRAM CACHE RAM 0.01 GB $1 $100 $10 $1000 Entry Cost
Why use MEMS?(cont.) • Volume • Examples Flash memory, 0.4 µm2 cell 100,000 10,000 3.5” Disk Drive 1000 Occupied volume [cm3] 100 10 Chip-sized data storage @ 10 GByte/cm2 1 0.1 0.1 1 10 100 1000 10,000 Storage Capacity [GByte]
Why use MEMS?(cont.) • Lower data latency • Why not EEPROM? $300 / GB EEPROM (Flash) DRAM $100 / GB Prediction 2008 $30 / GB Cost $ / GB $10 / GB MEMS Worst-Case Access Time (Rotational Latency) $3 / GB HARD DISK $1 / GB 100µs 10ns 1µs 10ms
Storage Device Design • 2 proposed models • Cantilever • “Moving media”
Read/Write tips Actuators Magnetic Media “Moving Media”
Bits stored underneath each tip “Moving Media” Read/write tips Media side view
Logistics • Area = 1 cm2 • 10,000 probe tips • Bit cell of 0.0025-0.0009 µm2 4 – 11 GB • Advantages / disadvantages
Data Layout • Cylinders • Tracks • Sectors • Logical block
Device Performance • timeservice=time seek+latencyrotate+timetransfer • MEMS • timeservice=time seek +timetransfer time seek,acceleration, turnaround time, settling time
Physical Characteristics • Bit Size • Access Velocity • Sled acceleration • Spring stiffness • Number of sleds • Number of active tips • Error rates
Performance Characteristics • Seek time • Settle time • Turnaround time • Peak bandwidth • Capacity • Power • Reliability
Example • Fast read-modify-write • No rotational latency Atlas 10K MEMS Read 0.14 0.13 Reposition 5.98 0.07 Write 0.14 0.13 Total 6.26 0.33
Sustained Data Rate 1.6 Mbits / sec * 1280 tips = 2048 Mbits / sec
Failure Management • MEMS devices will have internal failures • Tips will break during fabrication/assembly, use • Media can wear ECC can be both horizontal and vertical Could then use spares to regain original level of reliability
Performance Models • Generation 1 • Generation 2 • Generation 3 • Reference disk – Atlas 10k • Super disk
Power Utilization • Lower operating power • 100 mW for sled positioning • 1 mW per active tip • For 1000 active tips, total power is 1.1 watt • 50 mW standby mode • Fast transition from standby – 0.5 ms
Future Potential • Definite advantages • Portable applications • New low-cost entry point • Archival storage • Active storage devices • Throwaway devices • …
Problems? • Very little has been implemented • Power consumption? • Heat – kinetic energy? • Reliability? • Sturdiness? • Any other alternatives?
Conclusions • Potential to fill the RAM/Disk gap • Simulation results show • reductions in I/O stall times • overall performance improvement We’ll have to wait and see …