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Outline for today. Topic: MEMStore paper Administrative: No class on Wednesday!. MEMS-based Storage. David Nagle, Greg, Ganger, Steve Schlosser, and John Griffin http://www.chips.ece.cmu.edu/. What if a “disk drive” could …. Storage 10 Gbytes of data In the size of a penny

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outline for today
Outline for today
  • Topic: MEMStore paper
  • Administrative:
    • No class on Wednesday!
mems based storage

MEMS-based Storage

David Nagle, Greg, Ganger, Steve Schlosser, and John Griffin

http://www.chips.ece.cmu.edu/

what if a disk drive could
What if a “disk drive” could …
  • Storage 10 Gbytes of data
    • In the size of a penny
  • Deliver 100 MB – 1 GB/sec bandwidth
  • Deliver access times 10X faster than today’s drives
  • Consume ~100X less power than low-power disk drives
  • Integrate storage, RAM, and processing on the same die
    • The drive is the computer
  • Cost less than $10

http://www.chips.ece.cmu.edu

how do you put a disk drive on a chip
How do you put a “Disk Drive” on a chip?
  • Build storage using MEMS
    • MEMS are MicroElectricMechanicalSystems
      • Physical sensor and actuator systems with features measured in microns
      • Built using process technologies similar to current CMOS fabs
    • Enable co-location of nonvolatile storage, RAM and processing on same physical chip

http://www.chips.ece.cmu.edu

example
Example
  • The world\'s smallest guitar is 10 micrometers long –
    • about the size of a single cell -- with six strings each about 50 nanometers, or 100 atoms, wide. Made by Cornell University researchers from crystalline silicon, it demonstrates a new technology for a new generation of electromechanical devices. Photo by D. Carr and H. Craighead, Cornell.The above image (508 x 327 pixels) is the digital image created by the electron microscope, and is the highest-resolution version available.

http://www.chips.ece.cmu.edu

applications of mems
Applications of MEMS
  • Sensors
    • accelerometers
    • gyroscopes
  • Actuators
    • micromirror arrays for LCD projectors
    • heads for inkjet printers
    • optical switches
    • microfluidic pumps for delivering medicine

http://www.chips.ece.cmu.edu

mems based storage1

Read/Write

tips

Actuators

Magnetic

Media

MEMS-based Storage
  • On-chip Magnetic Storage - using MEMS for media positioning

http://www.chips.ece.cmu.edu

mems based storage2

Bits stored

underneath

each tip

MEMS-based Storage

Read/write

tips

Media

side view

http://www.chips.ece.cmu.edu

mems based storage3
MEMS-based Storage
  • Read/write probe tips

1 m

probe tip

group of six tips

100 m

http://www.chips.ece.cmu.edu

mems based storage4

Y

X

MEMS-based Storage

Media Sled

http://www.chips.ece.cmu.edu

mems based storage5

Y

X

MEMS-based Storage

Springs

Springs

Springs

Springs

http://www.chips.ece.cmu.edu

mems based storage6

Y

X

MEMS-based Storage

Anchor

Anchor

Anchors attach

the springs to

the chip.

Anchor

Anchor

http://www.chips.ece.cmu.edu

mems based storage7

Y

X

MEMS-based Storage

Sled is free

to move

http://www.chips.ece.cmu.edu

mems based storage8

Y

X

MEMS-based Storage

Sled is free

to move

http://www.chips.ece.cmu.edu

mems based storage9

Y

X

MEMS-based Storage

Springs pull

sled toward

center

http://www.chips.ece.cmu.edu

mems based storage10

Y

X

MEMS-based Storage

Springs pull

sled toward

center

http://www.chips.ece.cmu.edu

mems based storage11

Y

X

MEMS-based Storage

Actuator

Actuators pull

sled in both

dimensions

Actuator

Actuator

Actuator

http://www.chips.ece.cmu.edu

mems based storage12

Y

X

MEMS-based Storage

Actuators pull

sled in both

dimensions

http://www.chips.ece.cmu.edu

mems based storage13

Y

X

MEMS-based Storage

Actuators pull

sled in both

dimensions

http://www.chips.ece.cmu.edu

mems based storage14

Y

X

MEMS-based Storage

Actuators pull

sled in both

dimensions

http://www.chips.ece.cmu.edu

mems based storage15

Y

X

MEMS-based Storage

Actuators pull

sled in both

dimensions

http://www.chips.ece.cmu.edu

mems based storage16

Y

X

MEMS-based Storage

Probe tip

Probe tips

are fixed

Probe tip

http://www.chips.ece.cmu.edu

mems based storage17

Y

X

MEMS-based Storage

Probe tips

are fixed

http://www.chips.ece.cmu.edu

mems based storage18

One probe tip

per square

Sled only

moves over

the area of a

single square

Each tip

accesses data

at the same

relative position

Y

X

MEMS-based Storage

http://www.chips.ece.cmu.edu

why use mems based storage
Why Use MEMS-based Storage?

Capacity @ Entry Cost

  • Cost !
    • 10X cheaper than RAM
    • Lower cost-entry point than disk
      • $10-$30 for ~10 Gbytes
    • New product niches
    • Can be merged with DRAM & CPU(s)
  • Example Applications:
    • “throw-away” sensors / data logging systems infrastructure monitoring; e.g., bridge monitors, concrete pours, smart highways, condition-based maintenance, security systems, low-cost speaker-independent continuous speech recognition, etc.
    • Ubiquitous use in everyday world … every appliance will be smart, store information, and communicate

100 GB

HARD

DISK

MEMS

10 GB

1 GB

0.1 GB

DRAM

CACHE RAM

0.01 GB

$1

$100

$10

$1000

Entry Cost

http://www.chips.ece.cmu.edu

why not eeprom
Why Not EEPROM?
  • We have computers on a chip now - Embedded computers
    • Billions of embedded CPUs sold today
    • How are HI2PS2 different today’s “embedded computer”?
      • Currently nonvolatile memory is EEPROM (FLASH memory)
      • MEMS >> increase in nonvolatile mass memory (many GB)
  • EEPROM* Feature Size Scaling vs. Time:

1997 1999 2001 2003 2006 2009

NOR Cell Area (um2) 0.6 0.3 0.22 0.15 0.08 0.04 (density MB/cm2) 16 32 44 64 120 240

EEPROM cost $/MB $4 $2 $1.5 $1 $0.53 $0.27 (Best Case - no increase in fab cost / cm2)

  • Taking EEPROM prices as $0.27/MB --> 10GB = $2,700
    • For IC-Based Storage in 2009 we predict cost ~$25 / 10GB
      • > 100X better than EEPROM

* From Semiconductor Industries Association (SIA) Roadmap 1997

http://www.chips.ece.cmu.edu

why use mems based storage1
Why Use MEMS-based Storage?

Flash memory, 0.4 µm2 cell

  • Volume !
  • 10 GByte/cm2 = 65 GB/in2 density (100x CD-ROM)
  • 30 nm x 30 nm bit size
  • Example Applications:
      • Space / satellite use - store data when not in line of site act as packet buffer for communications satellites, etc.
      • Human portable applications - e.g., medical implants, super PDA
      • Law enforcement / monitoring devices / security surveillance

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]

http://www.chips.ece.cmu.edu

why use mems based storage2
Why Use MEMS-based Storage?
  • Lower Data Latency !
  • Conventional disk drives: worst-case rotational latency 5-11ms
  • IC-Based Mass Storage: depends on design - 100’s of ms possible
  • Example Applications
    • Transaction-processing storage, Non-volatile storage hierarchies, network-buffers

$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

http://www.chips.ece.cmu.edu

managing mems based storage

2500

2500

Media area

divided into

“regions”

Sector is

8 data bytes +

ECC + servo

Data stored

in “sectors”

of ~100 bits

ManagingMEMS-based Storage
  • MEMS Data Layout

http://www.chips.ece.cmu.edu

data layout
Data layout
  • Optimized for:
    • Sequential access
    • Local access

2500

1

2

3

  • Serpentine layout

http://www.chips.ece.cmu.edu

slide31

1

2

3

2500

Read-modify-write

example

http://www.chips.ece.cmu.edu

fast read modify write
Fast Read-Modify-Write
  • Disks must wait an entire disk rotation to perform a read-modify-write
    • MEMS devices can quickly turn around and write (or rewrite a sector)
    • Example: Read-modify-write of 8 sectors (4KBytes) in msecs

Atlas 10K MEMS

Read 0.14 0.13

Reposition 5.98 0.07

Write 0.14 0.13

Total 6.26 0.33

http://www.chips.ece.cmu.edu

x dimension settling time

Oscillations in Y

Oscillations in X

X-dimension Settling Time
  • Consider a simple seek

...

...

...

Why do we only

care about the

X dimension?

...

Sweep area of one probe tip

http://www.chips.ece.cmu.edu

x dimension settling time1

In Y, the oscillations

appear as slight

variations in velocity,

which can be

tolerated.

Oscillations in X

lead to off-track

interference!

Sled is moving

in Y

X-dimension Settling Time

Why do we only

care about the

X dimension?

http://www.chips.ece.cmu.edu

seek time from center
Seek Time from Center

0.7

0.6

0.5

Seek time (ms)

0.4

0.3

0.2

0.1

0

-1000

-500

0

500

1000

X displacement (bits)

http://www.chips.ece.cmu.edu

seek time from center1
Seek Time from Center

http://www.chips.ece.cmu.edu

the effect of settle time

Seek time in X

Seek time in Y

The Effect of Settle Time

0.7

with settling constant

without settling constant

0.6

0.5

Seek time (ms)

0.4

0.3

0.2

0.1

0

-1000

-500

0

500

1000

Displacement (bits)

http://www.chips.ece.cmu.edu

seek time without settle
Seek Time Without Settle

http://www.chips.ece.cmu.edu

slide47

Turn-around

Access data and then turn aroundand access same data

http://www.chips.ece.cmu.edu

slide48

Turn-around

Access data and then turn aroundand access same data

http://www.chips.ece.cmu.edu

slide49

Turn-around

Access data and then turn aroundand access same data

http://www.chips.ece.cmu.edu

slide50

Turn-around

Access data and then turn aroundand access same data

Turning

“Turn-around”,

No data is accessed

http://www.chips.ece.cmu.edu

slide51

Turn-around

Access data and then turn aroundand access same data

http://www.chips.ece.cmu.edu

slide52

Turn-around

Access data and then turn aroundand access same data

http://www.chips.ece.cmu.edu

slide53

Turn-around

Access data and then turn aroundand access same data

Turning

“Turn-around”,

No data is accessed

http://www.chips.ece.cmu.edu

os view of mems based storage
OS view of MEMS-based storage
  • High-level MEMS characteristics:
    • Long positioning times
    • High streaming rate
  • Logical block interface works well
    • Opportunities for device optimization, but convoluted tricks not necessary

http://www.chips.ece.cmu.edu

fast 2004 paper
FAST 2004 Paper
  • Specificity test – are the benefits of a policy or role MEMS-specific?
    • If fails (performance same when compared to fast disk),MEMStore considered just like a fast disk wrt this role or policy
  • Merit test
    • If MEMS-specific, is it worth it (>10% improvement)?
  • Standard Storage Interface (interoperability)
    • Linear array of logical blocks (512 bytes)
    • Exact mapping of LBN to physical media is hidden
  • Contract for the Standard Interface (performance model)
    • Sequential access is best
    • Access to nearby LBN is more efficient that distant
    • Ranges of LBN are interchangeable
  • Good qualitative arguments for MEMStores to be block-oriented and the contract stays valid
request scheduling

-MAX

0

MAX

Request scheduling

http://www.chips.ece.cmu.edu

request scheduling1
Request scheduling

Seek time in X

Seek time in Y

-MAX

0

MAX

http://www.chips.ece.cmu.edu

mems scheduling
MEMS scheduling

(first come, first served)

Saturation point

http://www.chips.ece.cmu.edu

mems scheduling1
MEMS scheduling

(shortest “seek time” first)

http://www.chips.ece.cmu.edu

mems scheduling2
MEMS scheduling

(shortest positioning time)

http://www.chips.ece.cmu.edu

disk scheduling
Disk scheduling

Curves saturate

in same order,

relative position

X-axis shift

http://www.chips.ece.cmu.edu

fast 2004 scheduling results
FAST 2004 Scheduling Results

SDF isShortestDistanceFirst

data layout1
Data layout
  • Basically as for disks
    • Sequential access >>> not sequential
    • Local access > not local
  • Some interesting differences
    • File size vs. physical location

http://www.chips.ece.cmu.edu

small requests

0.37 ms/move

in this subregion

0.42 ms/move

in this subregion

Small requests

http://www.chips.ece.cmu.edu

large requests 256kb

0

MAX

Large requests: 256KB
  • Transfer time dominates positioning time

Long seek

Short seek

http://www.chips.ece.cmu.edu

bipartite layout
Bipartite layout

Metadata or

small objects

Large/streaming objects

http://www.chips.ece.cmu.edu

fast 2004 memstore specific features
FAST 2004: MEMStore Specific Features
  • Tip – subset parallelism
  • 2D data structures
  • Quick turnarounds (read-modify-write operations)
  • Device scan

2D Data Structure Accesses

failure management
Failure Management
  • MEMS devices will have internal failures
    • Tips will break during fabrication/assembly … and during use
    • Media can wear
  • With multiple tips, data and ECC can be striped across the tips
    • ECC can be both horizontal and vertical
    • On tip or tip-media failure, ECC prevents data loss
    • Could then use spares to regain original level of reliability

http://www.chips.ece.cmu.edu

failure management1
Failure Management
  • MEMS devices will have internal failures
    • Tips will break during fabrication/assembly … and during use
    • Media can wear

Probe Tip

http://www.chips.ece.cmu.edu

failure management2

Spare Tip

Failure Management
  • MEMS devices will have internal failures
    • Tips will break during fabrication/assembly … and during use
    • Media can wear

Probe Tip

Spare Tip

http://www.chips.ece.cmu.edu

failure management3

Spare Tip

Failure Management
  • MEMS devices will have internal failures
    • Tips will break during fabrication/assembly … and during use
    • Media can wear

Probe Tip

Spare Tip

http://www.chips.ece.cmu.edu

mems in computer systems
MEMS in Computer Systems
  • MEMS-based storage device simulator
    • Uses first-order mechanics
  • Integrated into DiskSim
    • Models events, busses, cache
    • Compare against simulated disks
  • SimOS-Alpha
    • Full machine simulator with DiskSim as storage subsystem

http://www.chips.ece.cmu.edu

random workload 15x speedup
Random Workload - 15X Speedup

10,000 small random requests, 67% reads,

exponentially sized with mean 4KB.

10,000 small random requests, 67% reads,

exponentially sized with mean 4KB.

http://www.chips.ece.cmu.edu

random workload 15x speedup1

MEMS has small

positioning variability

Random Workload - 15X Speedup

10,000 small random requests, 67% reads,

exponentially sized with mean 4KB.

http://www.chips.ece.cmu.edu

postmark 5x speedup
PostMark - 5X Speedup

http://www.chips.ece.cmu.edu

mems based storage as disk cache

HP Cello trace

has 8 disks

10.4GB total capacity

Baseline MEMS

3 GB

1999 Disk

(Quantum Atlas 10K)

9 GB

MEMS-based Storage as Disk Cache

File System

MEMS

Cache

Disk

http://www.chips.ece.cmu.edu

baseline configuration
Baseline Configuration

File System

Disk

Disk

Disk

Disk

http://www.chips.ece.cmu.edu

disk cache configuration
Disk Cache Configuration

File System

MEMS

MEMS

MEMS

MEMS

http://www.chips.ece.cmu.edu

disk cache configuration1

MEMS

Cache

MEMS

Cache

MEMS

Cache

MEMS

Cache

Disk

Disk

Disk

Disk

Disk Cache Configuration

File System

http://www.chips.ece.cmu.edu

mems based storage as a disk cache
MEMS-based Storage As a Disk Cache

http://www.chips.ece.cmu.edu

file system managed layout
File System-managed Layout
  • File system could allocate data directly

File system

Disk

MEMS

  • Metadata
  • Small files
  • Paging
  • Large, streaming files

http://www.chips.ece.cmu.edu

low power disk drives
Low-power Disk Drives
  • IBM Travelstar 8GS

Command stream ends

3

Active

2

Power (W)

Perf Idle

40 ms

1

400 ms

2 s

Fast

Idle

Low power Idle

Standby

0

0

5

10

Time (s)

http://www.chips.ece.cmu.edu

mems based storage19

Standby

(not to scale)

1

Active

Power (W)

0

0

5

10

Time (s)

MEMS-based Storage
  • 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

http://www.chips.ece.cmu.edu

postmark
PostMark

3111

58

http://www.chips.ece.cmu.edu

postmark1
PostMark

Performance Idle

Active

Active

http://www.chips.ece.cmu.edu

netscape
Netscape

6097

349

http://www.chips.ece.cmu.edu

netscape1
Netscape

Lots of transitions

Largely idle

Active

http://www.chips.ece.cmu.edu

future of mems based storage
Future of MEMS-based Storage
  • Perfect for portable devices
    • Size, capacity, power

http://www.chips.ece.cmu.edu

mems based storage is on the way
MEMS-based Storage Is On the Way
  • Interesting new storage technology
    • Gigabytes of non-volatile data in a single IC
    • Sub-millisecond average access time
    • Low power
  • Can fill various roles
    • Augment memory hierarchy
    • Portable devices
    • Archival storage
    • Active storage devices

http://www.chips.ece.cmu.edu

mems based storage at cmu
MEMS-based Storage at CMU

lcs.web.cmu.edu/research/MEMS

[email protected]

http://www.chips.ece.cmu.edu

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