MEMS-based storage system

MEMS-based Storage System

Kim Tae Seok (2004.7.20.)

MEMS in terms of research topic

• Research Trend in OSLAB

2004 time

Web server/cache

Multimedia system

Flash memory

Low power systemUbiquitous Computing

MEMS-based storage?

MEMS-based storage system topic is in the infancy !!!

Contents

• What is MEMS(MEMS-based storage)?• Why MEMS-based storage?• MEMS-based storage structure• OS view of MEMS-based storage• The future for MEMS-based storage

What is MEMS(MEMS-based storage)?

The need of new storage technology

Disk

RAMCPU

time

speed

gab

cache

memory

gab

?

The RAM-to-disk performance gab

- 6 orders of magnitude in 2000

- widen by 50% per year

Alternatives to Disk

• Solid state storage• Flash memory• Ferro-electric (FeRAM)• Magnetic RAM (MRAM)• Polymer• Chalcogenic/Ovonicmaterials• Organics (protein, DNA)

• Non-rotating magnetic media• MEMS

• Small-format arrays (multiple disks in one package)

What is MEMS?

• Micro Electro Mechanical System• the integration of mechanical elements, sensors, actuators, and

electronics on a common silicon substrate through microfabrication technology.

• electronics parts : integrated circuit (IC) process (e.g., CMOS)• micromechanical parts : micromachining processes

• MEMS promises to make possible the realization of complete systems-on-a-chip.• Enable co-location of nonvolatile storage, RAM, network module

and processing on same physical chip• augments the decision-making capability with "eyes" and "arms", to

allow microsystems to sense and control the environment.

Applications of MEMS

• Ubiquitous use in everyday world!!!• Ongoing research

• Sensors/Actuators• accelerometers• micromirror arrays for LCD projectors• heads for inkjet printers• optical switches• …

• MEMS-based storage

Why use MEMS-based storage?

Why Use MEMS-based Storage?

• Cost

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

10X cheaper than RAM

Lower cost-entry point than disk

$10-$30 for ~10 Gbytes


• Volume

100,000

Occupiedvolume [cm3]

0.1 1 10 100 1000 10,0000.1

10100

100010,000

3.5” Disk Drive

Flash memory, 0.4 µm2 cell

Chip-sized data storage@ 10 GByte/cm21

Storage Capacity [GByte]

10 GByte/cm2

= 65 GB/in2

density (100x CD-ROM)

30 nm x 30 nm bit size


• Data latency

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

No rotation delay

10x faster access time than today’s disk drive


• 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• Cost less than $10• Integrate storage, RAM, and processing on the same die

Why Not EEPROM?

• We have computers on a chip now (Embedded computers)• Currently nonvolatile memory is EEPROM (FLASH memory)

• EEPROM Feature (size and cost)

• Taking EEPROM prices as $0.27/MB --> $2,700 / 10GB • For MEMS-based Storage in 2009 we predict cost ~$25 / 10GB

• > 100X better than EEPROM

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

MEMS-based storage is available now?

• MEMS-based storage devices are still several years away from commercialization• Design details are not revealed

• Many designs are possible• While design details for MEMS are differ, most use a similar media

sled design• Ongoing device development company

• IBM(Millipede), Hewlett-Packard, Kionix, Nanochip• http://www.zurich.ibm.com/st/storage/millipede.html

• Ongoing software research group• Computer Systems LAB. of Carnegie Mellon University

• http://www.lcs.ece.cmu.edu/research/MEMS• Feedback loop with MEMS device group

• Design parameter (e.g., the number of tips)

http://www.zurich.ibm.com/st/storage/millipede.html

http://www.zurich.ibm.com/st/storage/millipede.html

http://www.lcs.ece.cmu.edu/research/MEMS

Design parameter Example

• size : 1-1.5 cm2

• capacity : 2-10GB• power : 1-3W (during access)• avg. access time : 1-3ms (random)• bandwidth: 10-100MB/sec• many tradeoffs

• # of active tips, multiple sleds, etc• capacity vs. latency vs. power vs. bandwidth

MEMS-based storage structure

MEMS-based Storage

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

Read/Writetips

MagneticMedia

Actuators

MEMS-based Storage

Read/writetips

Media

Bits storedunderneath

each tipside view

MEMS-based Storage

Media Sled

X

Y

MEMS-based Storage

Springs Springs

SpringsSprings

X

Y

MEMS-based Storage

Anchors attachthe springs to

the chip.

Anchor Anchor

AnchorAnchor

X

Y

MEMS-based Storage

Sled is freeto move

X

Y

MEMS-based Storage

Springs pullsled toward

center

X

Y

MEMS-based Storage

X

Y

Springs pullsled toward

center

MEMS-based Storage

Actuators pullsled in bothdimensions

Actuator

Actuator

Actuator

Actuator

X

Y

MEMS-based Storage

Actuators pullsled in bothdimensions

X

Y

MEMS-based Storage

Probe tipsare fixed

Probe tip

Probe tip

X

Y

MEMS-based Storage

X

Y

Probe tipsare fixed

MEMS-based Storage

X

Y

Sled onlymoves overthe area of asingle square

One probe tipper square

Each tipaccesses dataat the same

relative position

ManagingMEMS-based Storage

• MEMS Data Layout

Sector is8 data bytes +ECC + servo

Media areadivided into“regions”

2500

2500

Data storedin “sectors”of ~100 bits

Read-modify-writeexample

1 2 3 2500…

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 MEMSRead 0.14 0.13Reposition 5.98 0.07Write 0.14 0.13Total 6.26 0.33

X-dimension Settling Time• Consider a simple seek

...

...

...

...

Sweep area of one probe tip

Oscillations in X

Oscillations in Y

Why do we onlycare about theX dimension?

X-dimension Settling Time

Oscillations in Xlead to off-track

interference!

In Y, the oscillationsappear as slight

variations in velocity,which can be

tolerated.

Sled is movingin Y

Why do we onlycare about theX dimension?

Seek Time from Center

00.10.20.30.40.50.60.7

-1000 -500 0 500 1000

Seek

tim

e (m

s)

X displacement (bits)

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

Disk scheduling

0

20

40

60

80

100

10 50 90 130 170 210

Mean arrival rate (Hz)

Ave

rage

resp

onse

tim

e (m

s) FCFSSSTFSPTF

MEMS scheduling

0

20

40

60

80

100

100 500 900 1300 1700 2100

Mean arrival rate (Hz)

Ave

rage

resp

onse

tim

e (m

s) FCFSSSTFSPTF

Curves saturatein same order,relative position

Disk vs. MEMS-based storage

• How to schedule requests?

in outprobe tip

Disk

One-dimension problem

MEMS

Two-dimensions problem

Data layout

• Basically as for disks• Sequential access >>> not sequential• Local access > not local

• Some interesting differences• File size vs. physical location

Small requests

0.42 ms/movein this subregion

0.37 ms/movein this subregion

Large requests: 256KB

• Transfer time dominates positioning time

0

1

2

3

4

Distance (in X)

Aver

age

resp

onse

tim

e (m

s)

0 MAX

Short seek Long seek

Bipartite layout

Metadata orsmall objects

Large/streaming objects

Failure Management

• MEMS devices will have internal failures• Tips will break during fabrication/assembly … and during use

• 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

Failure Management

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

Probe Tip

Spare Tip

Spare Tip

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

Random Workload - 15X Speedup

10,000 small random requests, 67% reads,exponentially sized with mean 4KB.

0

2

4

6

8

10

12

1999 Disk 2003 Disk MEMS

Storage Device Type

Ave

rage

Acc

ess

Tim

e (m

s)

MEMS has smallpositioning variability

MEMS-based Storage as Disk Cache

File System

Disk

MEMSCache

HP Cello tracehas 8 disks

10.4GB total capacity

1999 Disk(Quantum Atlas 10K)

9 GB

Baseline MEMS3 GB

Disk Cache Configuration

File System

Disk

MEMSCache

Disk

MEMSCache

Disk

MEMSCache

Disk

MEMSCache

MEMS-based Storage As a Disk Cache

02468

10121416

1999 Disk MEMS only 1999 Disk +MEMS Cache

Storage Device Type

Ave

rage

Acc

ess T

ime

(ms)

File System-managed Layout

• File system could allocate data directly

MEMS Disk

File system

• Metadata• Small files• Paging

• Large, streaming files

Perf Idle Fast

Idle Low power Idle Standby

Active

Low-power Disk Drives

• IBM Travelstar 8GS

Time (s)

Pow

er (W

)

0

1

2

3

0 5 10

Command stream ends

40 ms2 s400 ms

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

0.5 ms

Active

Time (s)

Pow

er (W

)

0

1

0 5 10

Standby(not to scale)

• Fast transition from standby

PostMark

0500

100015002000250030003500

Travelstar MEMSStorage Device Type

Ene

rgy

(Jou

les)

3111

58

PostMark

0500

100015002000250030003500

Travelstar MEMSStorage Device Type

Ene

rgy

(Jou

les)

Performance Idle

Active

Active

Conclusions

Future of MEMS-based Storage

• Perfect for portable devices• Size, capacity, power

System-on-a-Chip

• Filling memory gap• Operating system support

• Scheduling• Data layout• Fault management

• New applications• PDA, digital music, video, archival

storage

2 cm2 cm

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• Active storage devices

Research topic

• What applications are beneficial?• Developing new applications

• Where/how to use it in a system?• System architecture

• How can maximize it’s performance as a storage?• Using parallelism effectively• …

Conclusions

• MEMS-based storage • It is an exciting new technology :)

• Large capacity, low cost, low volume, low power,…• Block device (e.g., disk) background in OSLAB may be helpful. :)

• I/O scheduling, data layout…• But, it is not available now… :(

Reference

• [1] Schlosser, S., Griffin, J., Nagle, D., Ganger, G., Filling the Memory Access Gap: A Case for On-Chip Magnetic Storage. Technical Report CMU-CS-99-174, Carnegie Mellon University School of Computer Science, November 1999.

• [2] Schlosser, S., Griffin, J., Nagle, D., Ganger, G., Designing Computer Systems with MEMS-based Storage. In ASPLOS 2000, November 13-15, 2000.

• [3] L. Richard Carley, Gregory R. Ganger, and David F. Nagle, MEMS-Based Integrated-Circuit Mass-Storage Systems. in COMMUNICATIONS OF THE ACM November 2000, Vol.43, No.11.

• [4] Griffin, J., Schlosser, S., Ganger, G., Nagle, D., Operating Systems Management of MEMS-based Storage Devices. In OSDI 2000, October 23-25, 2000.

• [5] Griffin, J., Schlosser, S., Ganger, G., Nagle, D., Modeling and Performance of MEMS-Based Storage Devices. In Proceedings of SIGMETRICS 2000, June 18-21, 2000. Published as Performance Evaluation Review 28(1):56-65, June 2000.

Reference

• [6] Tara M. Madhyastha, Katherine Pu Yang, Physical Modeling of Probe-Based Storage. In Proceedings of the Eighteenth IEEE Symposium on Mass Storage Systems (April 2001).

• [7] Z.N.J. Peterson, S.A. Brandt and D.D.E. Long. Data Placement Based on the Seek Time Analysis of a MEMS-based Storage Device. A Work in Progress (WIP) at: the Conference on File and Storage Technologies (FAST), USENIX, 2002.

• [8] Pu Yang. Modeling Probe-based Storage Devices. Tehcnical report. Department of Computer Science, University of California Santa Cruz, June 2000. Master's thesis.

• [9] B. Hong, Exploring the Usage of MEMS-based Strorage as Metadata Storage and Disk Cache in Storage Hierarchy. Department of Computer Science, University of California Santa Cruz. 2003

• [10] Steven W. Schlosser, Jiri Schindler, Anastassia Ailamaki, and Gregory R. Ganger, Exposing and Exploiting Internal Parallelism in MEMS-based Storage. Carnegie Mellon University Technical Report CMU-CS-03-125, March 2003.

Reference

• [11] M. Uysal, A. Merchant, and G. Alvarez, Using MEMS-based stroage in disk arrays. Proc. of 2nd USENIX Conference on File and Storage Technologies, April 2003

• [12] Hailing Yu, Divyakant Agrawal, and Amr El Abbadi, Towards Optimal I/O Scheduling for MEMS-Based Storage. 20 th IEEE/11 th NASA Goddard Conference on Mass Storage Systems and Technologies (MSS'03) April 07 - 10, 2003 San Diego, California

• [13] H. Yu, D. Agrawal, and A. E. Abbadi, Tabular Placement of Relational Data on MEMS-based Storage Devices. In proceedings of the 29th Conference on Very Large Databases(VLDB), 680-693. September 2003

• [14] MEMS-based Storage Systems (including slides from OSDI, Sigmetrics and ASPLOS) ppt. Carnegie Mellon University School of Computer Science

MEMS-based storage system

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