mems based mass storage systems
DESCRIPTION
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?. - PowerPoint PPT PresentationTRANSCRIPT
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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?
• Cost
• Examples
0.01 GB
0.1 GB
1 GB
10 GB
100 GB
$1 $10 $100 $1000
CACHE RAM
DRAM
HARDDISK
Entry Cost
MEMS
Capacity @ Entry Cost
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Why use MEMS?(cont.)
• Volume
• Examples
100,000
Occupiedvolume [cm3]
0.1 1 10 100 1000 10,0000.1
10
100
1000
10,0003.5” Disk Drive
Flash memory, 0.4 µm2 cell
Chip-sized data storage@ 10 GByte/cm21
Storage Capacity [GByte]
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Why use MEMS?(cont.)
• Lower data latency
• Why not EEPROM?
Worst-CaseAccessTime
(RotationalLatency)
Cost $ / GB
$1 / GB
$3 / GB
$10 / GB
$30 / GB
$100 / GB
10ns 1µs 100µs 10ms
DRAM
HARD DISK
Prediction2008
$300 / GBEEPROM (Flash)
MEMS
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Storage Device Design
• 2 proposed models– Cantilever– “Moving media”
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“Moving Media”
Read/Writetips
Read/Writetips
MagneticMedia
MagneticMedia
ActuatorsActuators
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“Moving Media” Read/writetips
Read/writetips
MediaMedia
Bits storedunderneath
each tip
Bits storedunderneath
each tipside 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
• timeservice=time
seek+latencyrotate+timetransfer
• MEMS
– timeservice=time 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 MEMSRead 0.14 0.13Reposition 5.98 0.07Write 0.14 0.13Total 6.26 0.33
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Seek Time From Center
00.20.40.60.8
SeekTime(ms)
X500
0-500
-1000
YDisplacement
-5000
500Displacement1000
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Sustained Data Rate
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
1.80
0.20 1.00 1.80 2.60 3.40
Per-tip Data Rate (Mbits/sec)
Sus
tain
ed D
ata
Rat
e (M
bits
/sec
) 1.6 Mbits / sec * 1280 tips = 2048 Mbits / sec
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Sustained Data Rate
0.00
0.50
1.00
1.50
2.00
2.50
0.20 1.00 1.80 2.60 3.40 4.20 5.00
Per-tip Data Rate (Mbits/sec)
Sus
tain
ed D
ata
Rat
e (M
b/se
c)Baseline Decreased Bit Size Doubled Actuator Force
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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 verticalCould 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
0
2
4
6
8
10
12
1999 Disk 2003 Disk MEMS
Storage Device Type
Ave
rage
Acc
ess
Tim
e (m
s)
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Postmark
0
100
200
300
400
500
600
700
800
1999 Disk 2003 Disk MEMS
Storage Device Type
Ove
rall
Run
time
(s)
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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
We’ll have to wait and see …