MEMS Based Mass Storage Systems

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MEMS Based Mass Storage Systems
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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

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Fender?

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

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Example
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Why use MEMS?
Capacity _at_ 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
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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 _at_ 10 GByte/cm2
1
0.1
0.1
1
10
100
1000
10,000
Storage Capacity GByte
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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
10ns
100µs
1µs
10ms
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Storage Device Design

• 2 proposed models
• Cantilever
• Moving media

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Moving Media
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Moving Media
Read/write tips
Media
side view
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Logistics

• Area 1 cm2
• 10,000 probe tips
• Bit cell of 0.0025-0.0009 µm2
• ? 4 11 GB
• Advantages / disadvantages

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Data Layout

• Cylinders
• Tracks
• Sectors
• Logical block

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Device Performance

• timeservicetime seeklatencyrotatetimetransfer
• MEMS
• timeservicetime seek timetransfer
• time seek,acceleration, turnaround time, settling
  time

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Physical Characteristics

• Bit Size
• Access Velocity
• Sled acceleration
• Spring stiffness
• Number of sleds
• Number of active tips
• Error rates

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Performance Characteristics

• Seek time
• Settle time
• Turnaround time
• Peak bandwidth
• Capacity
• Power
• Reliability

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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

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Seek Time From Center
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Sustained Data Rate
1.6 Mbits / sec 1280 tips 2048 Mbits /
sec
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Sustained Data Rate
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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

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Performance Models

• Generation 1
• Generation 2
• Generation 3
• Reference disk Atlas 10k
• Super disk

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Random Workload - Microbenchmark
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Postmark
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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

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Future Potential

• Definite advantages
• Portable applications
• New low-cost entry point
• Archival storage
• Active storage devices
• Throwaway devices

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Problems?

• Very little has been implemented
• Power consumption?
• Heat kinetic energy?
• Reliability?
• Sturdiness?
• Any other alternatives?

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Conclusions

• Potential to fill the RAM/Disk gap
• Simulation results show
• reductions in I/O stall times
• overall performance improvement
• Well have to wait and see