How to calculate mttdl

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JurajP

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Sep 20, 2013
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Hi,
i have problem, how to calculate MTTDL for array RAID 10. I need it to understand for test. I haven't found any equations for it. So if you could help me, I'll be happy :).

I have 4x4TB discs in RAID 10.
Average data transfer rate = 146 MB/s
Average read seek time rate = 8.5ms
Average write seek time rate = 9.5ms
AFR (Annualized failure rate) = 1,168%
MTTF (MTBF) = 750 000 hours.
MTTR = 8 hours - teoretically.

And I need to calculate MTTDL. I've tried to use this: MTTDL = (MTBF^2) / ((N) * (N - 1) * MTTR), but I'm not sure, if i'm correct.

Thank you.
 
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Yes, i've found this. But there is no equation how to calculate it. And I don't what does "VOLUME" mean. What should I enter.
 
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See here for a definition of a volume: http://en.wikipedia.org/wiki/Volume_%28computing%29

"In the context of computer operating systems, a volume or logical drive is a single accessible storage area with a single file system, typically (though not necessarily) resident on a single partition of a hard disk. Although a volume might be different from a physical disk drive, it can still be accessed with an operating system's logical interface. However, a volume differs from a partition. In Linux systems, volumes are usually handled by the Logical Volume Manager or the Enterprise Volume Management System and manipulated using mount(8). In NT-based versions of Microsoft Windows, volumes are handled by the kernel and managed using the Disk Management MMC snap-in."
 
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I read both articles, but I'm confused a little bit. It's very abstract. So I've created this equation from it:

MTTDL = MTBF ^ 2 / (2*N * MTTR), where N is number of discs, in my case 4 discs.
 
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