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Proposed Disk Array With 99.999% Availablity For 4 Years, Sans Maintenance

Posted by timothy on from the with-enough-disks-all-rooms-are-full dept.

Thorfinn.au writes with this paper from four researchers (Jehan-François Pâris, Ahmed Amer, Darrell D. E. Long, and Thomas Schwarz, S. J.), with an interesting approach to long-term, fault-tolerant storage: As the prices of magnetic storage continue to decrease, the cost of replacing failed disks becomes increasingly dominated by the cost of the service call itself. We propose to eliminate these calls by building disk arrays that contain enough spare disks to operate without any human intervention during their whole lifetime. To evaluate the feasibility of this approach, we have simulated the behaviour of two-dimensional disk arrays with N parity disks and N(N – 1)/2 data disks under realistic failure and repair assumptions. Our conclusion is that having N(N + 1)/2 spare disks is more than enough to achieve a 99.999 percent probability of not losing data over four years. We observe that the same objectives cannot be reached with RAID level 6 organizations and would require RAID stripes that could tolerate triple disk failures.

2 of 258 comments (clear)

  1. Not my anecdotal experience by futuresheep · · Score: 5, Interesting

    Just a few things I thought of while looking at this study:

    The authors are using Backblaze data. Backblaze uses consumer grade SATA disk which isn't going to be as reliable as the Enterprise SATA/SAS disk we would use.

    I'm willing to bet that none of the authors of this paper have ever had to pay for colocated rack space, power, and cooling either, they've just doubled the RU that I need for storage. At $1500.00 - $2000.00 per rack that adds up.

    Doubling the rack space for storage I need so I can avoid a few service calls by my storage vendor over 5 years simply isn't efficient.

    We've installed close to 500TB of archival storage using commodity hardware and 2-3TB Nearline SAS. We have maybe 3 hand and eyes calls per year for disk replacement.

    Anyway - just rambling.

  2. Trust by HideyoshiJP · · Score: 5, Interesting

    I don't trust anybody who has published a document with the title "C:\Users\Jehan-Francois Paris\Documents\ADAPT15\Case3.doc." Not even in .docx format. Tsk tsk.