Reliability of mems based storage enclosures
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Reliability of MEMS-Based Storage Enclosures. Bo Hong, Thomas J. E. Schwarz, S. J. * Scott A. Brandt, Darrell D. E. Long. Storage Systems Research Center University of California, Santa Cruz *Also Santa Clara University, Santa Clara, CA. Spring. MEMS Storage Technology.

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Reliability of MEMS-Based Storage Enclosures

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Reliability of mems based storage enclosures

Reliability of MEMS-Based Storage Enclosures

Bo Hong, Thomas J. E. Schwarz, S. J.*

Scott A. Brandt, Darrell D. E. Long

Storage Systems Research Center

University of California, Santa Cruz

*Also Santa Clara University, Santa Clara, CA


Mems storage technology

Spring

MEMS Storage Technology

  • Micro-Electro-Mechanical Systems (MEMS) storage

    • A promising alternative secondary storage technology

    • Hardware Research: IBM, HP, CMU, Nanochip

    • Magnetic storage, but very different mechanics


Mems storage technology1

MEMS Storage Technology

  • MEMS-based storage vs. Magnetic Disk

    • Provides non-volatile storage, too.

    • Delivers 10 * faster access time (< 1 ms)

    • Delivers higher bandwidth (100 MB – 1 GB/s)

    • Small (size of penny, cent)

    • Consumes 100* less power

    • Costs ~10 USD per device

    • Expected to be more reliable

    • Stores limited amount of data per device (3-10 GB)

  • A serious alternative to disk drives, in particular for mobile computing applications


Reliability implication of mems based storage

Reliability Implication of MEMS-based Storage

  • Storage systems built from MEMS-based storage …

    • Require more MEMS devices

      • At least 10 times the number of disks to meet capacity requirements

    • Require more connection components

  • Reliability implication

    • More components, hence (?) lower reliability


Mems storage enclosure

MEMS Storage Enclosure

  • Our proposal: MEMS Enclosures

    • A device with dozens of MEMS

    • Single interface to rest of system

    • Might be serviceable, but service calls during economic lifetime should be very rare

Interface


Mems storage enclosures

MEMS Storage Enclosures

  • Reliability an issue:

    • MTTF 1- 2 years without redundant data storage

  • Uses RAID Level 5 technology with distributed sparing

    • Additional k spares

  • Calls for service when necessary

    • i.e. when we run out of spares

  • Organization and number of spares can

    • Decrease the data recovery time and thus improve reliability

    • Reduce human interference

      • No errors servicing

      • Reduce maintenance costs


Mems enclosure reliability

MEMS Enclosure Reliability

  • Measure MTBF for enclosures

    • Without replacing spares

    • With replacing spares (service calls)

      • Determine number of failures that trigger a service call

      • Mandatory replacement: no redundancy left

      • Preventive replacement: no spare left


Mems enclosure reliability without replacement

MEMS Enclosure Reliability without Replacement

5 spares

8.1 Yrs

4 spares

6.9 Yrs

3 spares

5.8 Yrs

Disk

23 Yrs

Disk

11.5 Yrs

2 spares

4.6 Yrs

1 spare

3.5 Yrs

  • MTTFDISK = 11.5 or 23 yrs

  • MTTFMEMS = 23 yrs

  • 19 data + 1 parity + k dedicated spares

  • 15-minute data recovery

No spare

2.3 Yrs

  • MTTF is not enough to measure reliability of enclosures without repairs

  • Instead: focus on data reliability during the economic lifetimes (3-5 years) of enclosures


Mems enclosures with replacement

Preventive replacement

Mandatory replacement

MEMS Enclosures with Replacement

  • Markov model for a MEMS enclosure with N data, one parity, and one dedicated spare devices

    • N – Normal; D – Degraded; DL – Data Loss

    • 1/ – MTTFMEMS (in tens of years)

    • 1/µ – Mean Time Between Recovery (in minutes)

    • 1/ – Mean Time Between Replacement (in days, weeks)

  • Preventive and mandatory replacement


Mems enclosure reliability with replacement

MEMS Enclosure Reliability with Replacement

1, 2, 3 – Number of spares

Preventive + mandatory

3

2

1

Mandatory

3

2

1

No spare

  • Preventive replacement increases reliability and reduces replacement urgency


Mems enclosure reliability1

MEMS Enclosure Reliability

  • Dedicated Sparing

    • Replace all data from a failed MEMS on a single spare MEMS

  • Distributed Sparing

    • Every spare contains

      • Client data

      • Parity data

      • Spare space


Distributed sparing menon and mattson 1992

X

After MEMS 4 fails

  • Shorter data recovery time

  • More devices can fail

Distributed Sparing [Menon and Mattson 1992]

Before failure


Reliability comparison dedicated sparing vs distributed sparing

Dedicated

2

1

2

1

Reliability Comparison: Dedicated Sparing vs. Distributed Sparing

1, 2– Number of spares

Preventive + mandatory

Mandatory

Dedicated

No spare

Compare with following slide


Reliability comparison dedicated sparing vs distributed sparing1

2

1

2

1

Reliability Comparison: Dedicated Sparing vs. Distributed Sparing

1, 2– Number of spares

  • Distributed sparing only better at short replacement times when using preventive replacement

Distributed

Preventive + mandatory

Dedicated

Mandatory

Dedicated &

Distributed

No spare


Durability of mems storage enclosures

Durability of MEMS Storage Enclosures

  • All about economy

    • How long can MEMS enclosures work without repairs?

    • How often do they need repairing in the first 3-5 years?

    • How does replacement policies affect maintenance frequency?

  • # of failures an enclosure with k spares can tolerate before the (m+1)th repair is scheduled (m >= 0):

    • (m + 1) × k, under the preventive replacement policy

    • (m + 1) × (k + 1), under the mandatory replacement policy


Durability of mems storage enclosures1

Durability of MEMS Storage Enclosures

10 failures

Probabilities that a MEMS storage enclosure has up to k failure during (0, t]

6 failures

8 failures

Disk

23 Yrs

4 failures

1 failure

2 failures

No failure

  • First year survivability: 95.7% of disk vs. 98.8% of MEMS enclosures with two spares

  • Chance that MEMS enclosure with four spares requires more than one service in five years: 3.5% (preventive) vs. 0.6% (mandatory)


Related work

Related Work

  • MEMS-based storage technology development

    • IBM, HP, CMU CHI2PS, Nanochip

  • Digital Micromirror Devices by TI

    • Reported Mean Time Between Failure: 650,000 hours [Douglass]

  • RAID reliability

    • Dedicated sparing [Dunphy et al.]

    • Distributed sparing [Menon and Mattson]

    • Parity sparing [Reddy and Banerjee]

  • Disk failure prediction

    • S.M.A.R.T (Self-Monitoring Analysis and Reporting Technology)


Summary

Summary

  • Reliability of MEMS storage enclosures

    • Can be more reliable than disks even without failed device replacement

    • Highly reliable when using preventive replacement

    • Dedicated sparing and distributed sparing provide comparable or almost identical reliability

  • Economy of MEMS storage enclosures

    • Preventive replacement trades more maintenance services for higher reliability


Thank you

Thank You!

  • Acknowledgements

    • Dave Nagle, Greg Ganger, CMU PDL

    • The rest of the UCSC SSRC

  • More information:

    • http://ssrc.cse.ucsc.edu

    • http://ssrc.cse.ucsc.edu/mems.shtml

  • Questions?


Backup slides

Backup Slides


Mems storage technology2

MEMS Storage Technology

  • Micro-Electro-Mechanical Systems (MEMS) storage

    • A promising alternative secondary storage technology

    • Hardware Research: IBM, HP, CMU, Nanochip

  • Radical differences between MEMS storage and magnetic disk technologies


Mems storage device characteristics

Predicted Performance in 2005

MEMS Storage Device Characteristics

  • Physical size: 1 – 2 cm2

  • Recording density: 250 – 750 Gb/in2

7GB/s

DRAM

6GB/s

0.5–2 GB

$100-$200/GB

5GB/s

Throughput

4GB/s

3GB/s

MEMS

2GB/s

3–10 GB

$5-$50/GB

100–500 GB

$1-$2/GB

1GB/s

DISK

1ns

10ns

100ns

1us

10us

100us

1ms

10ms

Access Latency


Mems storage device

Spring

Y

X

MEMS Storage Device


Durability of mems storage enclosures2

Durability of MEMS Storage Enclosures

10 failures

Probabilities that a MEMS storage enclosure has up to k failure during (0, t]

6 failures

8 failures

Disk

23 Yrs

4 failures

1 failure

2 failures

No failure


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