Measuring the Cost of Reliability in Archival Systems James Byron - - PowerPoint PPT Presentation

Measuring the Cost of Reliability in Archival Systems

James Byron Center for Research in Storage Systems University of California, Santa Cruz

CRSS Confidential

Overview

❖ Motivation & Goals ❖ Analysis: HDD Lifespan ❖ Archival Reliability and Cost ❖ Conclusion

2

CRSS Confidential

Motivation

❖ Changing technology and demands for archival storage

➢

Changing storage technologies over time

➢

Expectation for predictably reliable and cost-effective storage

❖ Opportunity to meet future demand

3

CRSS Confidential

Goals

❖ Provide insights on development of next-gen storage technologies ❖ Propose designs for better archival systems ❖ Create tool to aid long-term planning

➢

How to plan for reliability as devices change?

4

CRSS Confidential

Overview

❖ Motivation & Goals ❖ Analysis: HDD Lifespan ❖ Archival Reliability and Cost ❖ Conclusion

5

CRSS Confidential

Analysis: HDD Lifespan

❖ Inquire into changes in HDD usage patterns ❖ Backblaze data covers 2013 to 2020

➢

Date drives added and removed

➢

Failure or retirement

❖ Observe how retirement rate changes as devices age ❖ Observe how device reliability affected by its age and generation

6

CRSS Confidential

Analysis: HDD Lifespan

❖ Plot retirement and failure rates ❖ Failure rate increases after 5 years of operation ❖ Retirement rate not predicated by increase in failure rate

7

CRSS Confidential

Analysis: HDD Lifespan

❖ Days to reach various drive failure rates by year ❖ Larger numbers (more days) are better ❖ Improvement in HDD reliability 2013-2017

8

Failure Rate 2013 2014 2015 2016 2017 2018 1% 67 143 168 268 332 252 2% 208 332 357 565 589 440 3% 394 503 554 948 745 582 4% 491 684 721 1349 1104

• 5%

618 816 941

• 10%

1195

• 15%

1793

CRSS Confidential

Analysis: HDD Lifespan

❖ How would longer-lasting HDDs affect archival costs? ❖ How do different storage technologies compare in terms of cost and reliability?

9

CRSS Confidential

Overview

❖ Motivation & Goals ❖ Analysis: HDD Lifespan ❖ Archival Reliability and Cost ❖ Conclusion

10

CRSS Confidential

Simulation Model

❖ Implemented an archival system simulator ❖ Model devices, rates of development, device failures ❖ Simulate designs with various amounts of RAID parity for each device ❖ Compare systems based on cost, reliability, and device type ❖ 25 year simulation period

11

CRSS Confidential

Cost of Reliability

❖ Assumptions used in simulation ❖ Archival data growth

➢ 1PB of data growing 30% annually

❖ Storage device capacity growth

➢ Each following historical trends ➢ Growth rate slows with time ➢ DNA’s growth continues unabated

12

CRSS Confidential

Cost of Reliability

❖ Comparing cost for “nines” of reliability ❖ Tape

➢ Optimistic stable AFR: 0.000075% ➢ Pessimistic growing AFR: 0.3%

13

CRSS Confidential

Cost of Reliability: HDD

❖ How much could be saved if HDDs lasted longer? ❖ How long should we keep HDDs? ❖ 7-9 years is optimal for HDDs with growing failure rates ❖ 11+ years is best for HDDs with stable failure rates ❖ 10% cost difference

14

CRSS Confidential

Experiments: Device Design

❖ How will changes in design affect storage technologies for reliable archival storage? ❖ Example: Dysan Disk Pack (c. 1970), HDD (c. 1990), Iomega Jaz (c.1996)

15

CRSS Confidential

HDD With Separable Platters

❖ How would HDD cost change with development of removable platters? ❖ 20% savings for 3-year upgrade cycle ❖ 42% savings for 1-year upgrade cycle

16

CRSS Confidential

SSD Development and Reliability

❖ Is it more important to have high reliability or capacity growth for SSDs? ❖ Double AFR for SSDs (left) correlates with 8% increase in cost ❖ Extending SSD development apace for 3 additional years into future (right) reduces cost 52%

17

CRSS Confidential

Tape With Higher AFR

❖ How will tape be affected if its reliability decreases with its increasing capacity? ❖ 10x increase in AFR correlates to an 81% cost difference

18

CRSS Confidential

Archival Glass

❖ How is the cost of glass affected by drive cost? ❖ 10x increase in read drive cost increases cost by 78% ❖ Only slight cost increase for added reliability

19

CRSS Confidential

Archival Synthetic DNA

❖ Is it better to have high capacity or a flexible design for DNA? ❖ DNA molecules

➢ Vary capacity ➢ Also vary forward compatibility of DNA with drives

❖ 100x capacity increase reduces cost by 68% ❖ Forward compatibility reduces cost by 60%

20

CRSS Confidential

Overview

❖ Motivation & Goals ❖ Analysis: HDD Lifespan ❖ Archival Reliability and Cost ❖ Conclusion

21

CRSS Confidential

Conclusion

❖ Improving HDD reliability could improve its competitive position ❖ Tape remains cost-effective across a range of reliability scenarios ❖ SSD becomes more competitive with higher capacity, even with lower reliability ❖ Glass and DNA are promising for archival storage

22

CRSS Confidential Thank You Contact James Byron jbyron@ucsc.edu

23