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Proposed Disk Array With 99.999% Availablity For 4 Years, Sans Maintenance
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.
So I tried to view the PDF, and it says "can't use the plugin, it causes problems on our server". So I figured I'd just download the file with wget instead. Nope, 403 forbidden.
Looks like fetch works though. If anybody else has trouble getting the file, try my local mirror.
I read the internet for the articles.
Many high end equipment does have fairly large capacitors to allow enough power off time to do a clean power off.
I remember back in the 1990's some PC Centric folks were looking in a Sun Workstation they were surprised about all the large capacitors that were on the motherboard. In short it gives the system enough time finish its final calculation before the power goes out.
If something is so important that you feel the need to post it on the internet... It probably isn't that important.
Yeah, we get it. You like to deal with cutting-edge stuff. Now get off my lawn.
Sent from my Commodore 64.
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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.
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.
Sloppy calculation tip: 24*365 = 10000.
If you're Sloppy enough to accept that premise, then at 10 cents/KWHr, a Watt costs a dollar per year. It makes your $28 turns into $32, but hey, close enough. When I'm shopping, I can add up lifetime energy costs really fast, without actually being smart. Nobody ever catches on!
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This is how we're going bring our keepers to their knees, and eventually break out of the Matrix. We spend imaginary money on imaginary storage and then put all sorts of high-entropy stuff on it and run calculations to verify that it's really working, but they have to spend actually real resources, to emulate it.
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