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Graham Perrin's List: reliability of hard disk, optical disc and flash media

5th USENIX Conference on File and Storage Technologies – Abstract

www.usenix.org/...schroeder.html - Preview

Diigo 9723 non-cached 2009 on 2009-01-18
- field-gathered disk replacement data from a number of large production systems, including high-performance computing sites and internet services sites
- annual disk replacement rates typically exceed 1%, with 2-4% common and up to 13% observed on some systems.
- 5 more annotations...
- - field replacement is a fairly different process than one might predict based on datasheet MTTF
  - early onset of wear-out degradation
  - replacement rates in our data grew constantly with age
  - assumed not to set in until after a nominal lifetime of 5 years
  - one instance of a customer rejecting an entire population of disks as a bad batch, in this case because of media error rates
5th USENIX Conference on File and Storage Technologies - Paper

db.usenix.org/...index.html - Preview

Diigo 9723 non-cached 2009 on 2009-01-18
- 7 Conclusion
- As a first step
- 5 more annotations...
- - analyzed disk replacement data from a number of
    large production systems, spanning more than 100,000 drives from
    at least four different vendors, including drives with SCSI, FC and
    SATA interfaces
  - For drives less than five years old, field replacement rates were larger
    than what the datasheet MTTF suggested by a factor of 2-10
    
    Add Sticky Note
  - For five to eight year old drives, field replacement rates were a factor of 30 higher than what the datasheet
    MTTF suggested
    
    Add Sticky Note
  - a continuous increase in replacement
    rates, starting as early as in the second year of operation.
  - anecdotal evidence
    that bad batches are not unique to SATA disks
Flash memory data recovery

www.cnwrecovery.co.uk/...flash_memory.html - Preview

Diigo 9723 non-cached 2009 on 2009-01-18
- Flash memory comes in several different physical packages
- without an external battery and with no moving parts, are extremely robust
- 1 more annotations...
- - Unless the chip is actually physically, or electrically damaged, CnW has a very high recovery success rate
FAQ CD & DVD

www.cnwrecovery.co.uk/...faq_cd___dvd.html - Preview

Diigo 9723 non-cached 2009 on 2009-01-18
- Q) Why are disks unreadable
  
  A) There are many answers
- physical damage
FAQ Disks

www.cnwrecovery.co.uk/...faq_disks.html - Preview

Diigo 9723 non-cached 2009 on 2009-01-18
- Q This disk is not spinning, can you help?
  
  A The answer is probably no.
- Q Why do files get lost?
  
  A There are more answers to this than days in a year, but typical reasons include
  
  Operator error
  Accidental deletion
  Operating system failure
  Accidental formatting
  Modifying partitions
  Hard disk failure, or partial failure
  Software crashing
  Power glitch
  Physical shock
  Virus (actually this is very rare)
Tips on preventing of data loss

www.cnwrecovery.co.uk/...prevention.html - Preview

Diigo 9723 non-cached 2009 on 2009-01-18
- There are several reasons for data loss, and below are the the most common ones
  
  Accidental deletion and other operator errors
  Hardware failure
  Physical loss of media, can include theft, fire, flood
  Viruses
  Malicious deletion of data
  Operating system corruption
  Damage after a power cut, or computer failure
  Something unexpected happening
Storage Best Practices and Resiliency Guide

Chris Lueth and Haripriya, NetApp
TR-3437

media.netapp.com/...tr-3437.pdf - Preview

unread Portable Document Format 2009 on 2009-01-18
MTTF versus MTBF

www.relex.com/...art_mttf.asp - Preview

Diigo 9723 non-cached 2009 on 2009-01-18 and saved by 2 people
- for a non-repairable system, MTTF is equivalent to the mean of
  its failure time
- While MTBF is one of the most widely used metrics in reliability engineering, it is also one
  that causes a great deal of confusion
- 3 more annotations...
- - After restoration, the system may not be as good as new
  - In most standards, MTBF is used to represent the mean time before
    failure
    
    Add Sticky Note
  - Even if a standard defines MTBF as the mean time between failures, it inherently
    means MTTF because MTTR is almost negligible
    
    Add Sticky Note
Reliability 101 Part I: Reliability Concepts and Terminology

www.relex.com/...art_reliability101_1.asp - Preview

Diigo 9723 non-cached 2009 on 2009-01-18
- The average time to failure for a system that is not repairable
- Mean Time To Failure (MTTF)
- 3 more annotations...
- - Reliability
    The probability that the item will perform a required function without
    failure under stated conditions for a stated period of time. Reliability is significant because it
    takes into account time.
  - reliability is expressed as a
    probability, it is always a value between 0 and 1.
  - Unreliability is the complement of reliability. If your reliability
    is 0.9, the unreliability is equal to 0.1
Re: RAID is not a backup!

lists.apple.com/...msg00166.html - Preview

disk storage Diigo 9723 non-cached RAID 2009 on 2009-02-08
- Compared to other physical formats, disk is ridiculously fragile and easily
  corrupted/destroyed even when powered off
- begging for disaster, because
  it's not designed to work that way
Hard Disk MTBF: Where's the Reliable Reliability Data? - News and Analysis by PC Magazine

www.pcmag.com/...0,2817,2105613,00.asp - Preview

Diigo 9723 non-cached 2009 on 2009-01-18
- disk replacement rates are much higher than predicted
- SMART (self-monitoring, analysis and reporting technology) code in hard drives and storage management software—long touted by the industry as the best predictor of disk failure—was mostly a security blanket
  Add Sticky Note
- 1 more annotations...
- - MTBF is just a statistical measure. We're not supposed to believe it.
Hard Disk MTBF: Flap or Farce?

www.eweek.com/...Hard-Disk-MTBF-Flap-or-Farce - Preview

Diigo 9723 non-cached 2009 on 2009-01-18
- annual disk replacements rates were more in the range of 2 to 4 percent
- as high as 13 percent for some sites
- 1 more annotations...
- - failure prediction models based on SMART parameters alone are likely to be severely limited in their prediction accuracy, given that a large fraction of our failed drives have shown no SMART error signals whatsoever
Page 2 - Hard Disk MTBF: Flap or Farce?

www.eweek.com/...1 - Preview

Diigo 9723 non-cached 2009 on 2009-01-18
- The current MTBF model isnt accounting accurately for how drives are handled in the field and how they function inside systems
- IT budgets must include a line item for regular replacement of hard disks
Everything you know about disks is wrong - Computerworld Blogs

blogs.computerworld.com/5038 - Preview

Diigo 9723 non-cached 2009 on 2009-01-18
- Annual Failure Rates were quite a bit higher than vendor MTBF specs suggest
- the best the Googlers observed was 1.7% in the first year, rising to over 8.6% in the third year
- 5 more annotations...
- - If you get one of these errors, replace your drive, but not getting one doesn't mean you are safe. SMART is simply not reliable
  - low utilization drives having slightly higher failure rates than high ulization ones.
  - failure rates do not increase when the average temperature increases
  - observed ARRs [Average Replacement Rate] range from 0.5% to as high as 13.5%. . . . up to a factor of 15 higher than datasheet AFRs. Most commonly, the observed ARR values are in the 3%range
  - Drives are mechanical devices and wear out like machines
StorageMojo » Everything You Know About Disks Is Wrong

storagemojo.com/...-you-know-about-disks-is-wrong - Preview

Diigo 9723 non-cached 2009 on 2009-01-18 and saved by 2 people
- Maybe consumer stuff gets kicked around more
- significant early onset of wear-out degradation
- 4 more annotations...
- - drives just wear out steadily
  - Instead replacement rates seem to steadily increase over time
  - Drives get old, fast
  - 99 Responses
StorageMojo » Google’s Disk Failure Experience

storagemojo.com/...oogles-disk-failure-experience - Preview

Diigo 9723 non-cached 2009 on 2009-01-18 and saved by 2 people
- drives look more reliable than what you and I see
- results of accelerated life testing
- 11 more annotations...
- - Vendors typically look at two types of data
  - don’t do a good job of reflecting real world usage
  - a drive tester consistently “green lights” a unit that invariably fails in the field
  - a miracle if you see them in real life.
  - your disk drive might crash without warning at any time
  - SMART can warn you about some problems, but miss others, so you can’t rely on it. So don’t
  - little correlation between disk workload and failure rates
  - don’t worry about doing those daily backups to disk and other I/O intensive work
    
    Add Sticky Note
  - failure rates do not increase when the average temperature increases
  - SOHO users, consider replacing 3 year old disks, or at least get serious about back up.
  - 24 Responses
StorageMojo » NetApp Weighs In On Disks

storagemojo.com/...netapp-weighs-in-on-disks - Preview

Diigo 9723 non-cached 2009 on 2009-01-18 and saved by 2 people
- Failure rates are several times higher than reported by drive companies
- YMMV and often will if you deploy these disks in anything but the mildest of eval / demo lab environments
- 2 more annotations...
- - consumer-class drives’ personality is determined by firmware that assumes the drive is isolated inside a laptop or desktop and cannot rely upon parity information stored on adjacent (peer) drives to recover from a partial or full error condition. Consequently, consumer drives exhibit “Type A” personalities as they heroically go offline for non-deterministic periods of time (a few seconds or many minutes), to “take charge” of the situation and perform various pre-programmed techniques attempting to resolve bad blocks, media / checksum errors, etc…
  - many circumstances not restricted to age, environmentals (NVH), power & cooling, or even electro-mechanical behavior of drive peers within the same array, which can render a drive unusable – and eventually failed
Hard disk drive - Wikipedia, the free encyclopedia

en.wikipedia.org/...Hard_disk_drive - Preview

storage 2009 on 2009-02-08 and saved by 2 people
- the head literally drags along the disk's surface until the air bearing is established

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Graham Perrin

18 items | 32 visits

Updated on 2009-02-08
Created on 2009-01-18

Category: Computers & Internet

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Graham Perrin's List: reliability of hard disk, optical disc and flash media

5th USENIX Conference on File and Storage Technologies – Abstract

5th USENIX Conference on File and Storage Technologies - Paper

Flash memory data recovery

FAQ CD & DVD

FAQ Disks

Tips on preventing of data loss

Storage Best Practices and Resiliency Guide

MTTF versus MTBF

Reliability 101 Part I: Reliability Concepts and Terminology

Re: RAID is not a backup!

Hard Disk MTBF: Where's the Reliable Reliability Data? - News and Analysis by PC Magazine

Hard Disk MTBF: Flap or Farce?

Page 2 - Hard Disk MTBF: Flap or Farce?

Everything you know about disks is wrong - Computerworld Blogs

StorageMojo » Everything You Know About Disks Is Wrong

StorageMojo » Google’s Disk Failure Experience

StorageMojo » NetApp Weighs In On Disks

Hard disk drive - Wikipedia, the free encyclopedia

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