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? The world's smallest guitar is 10 micrometers long – Made by Cornell University researchers from crystalline silicon

Example

Why use MEMS? Cost Examples 0.01 GB 0.1 GB 1 GB 10 GB 100 GB $1 $10 $100 $1000 CACHE RAM DRAM HARD DISK Entry Cost MEMS Entry Cost

Why use MEMS?(cont.) Volume Examples 100,000 Occupied volume [cm 3 ] , , ” Disk Drive Flash memory, 0.4 µm 2 cell Chip-sized data 10 GByte/cm 2 1 Storage Capacity [GByte]

Why use MEMS?(cont.) Lower data latency Why not EEPROM? 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

Storage Device Design 2 proposed models –Cantilever –“Moving media”

“Moving Media” Read/Write tips Read/Write tips Magnetic Media Magnetic Media Actuators

“Moving Media” Read/write tips Read/write tips Media Bits stored underneath each tip Bits stored underneath each tip side view

Logistics Area = 1 cm 2 10,000 probe tips Bit cell of µm 2  4 – 11 GB Advantages / disadvantages

Data Layout Cylinders Tracks Sectors Logical block

Device Performance time service =time seek +latency rotate +time transfer MEMS –time service =time seek +time transfer 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 10KMEMS Read Reposition Write Total

Seek Time From Center

Sustained Data Rate 1.6 Mbits / sec * 1280 tips = 2048 Mbits / sec

Sustained Data Rate

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

Random Workload - Microbenchmark

Postmark

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 …