tryllz

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About tryllz

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  1. Thanks for the reply from what I understand is that calculating availability for 1 disk is not the same as calculating for the disk array, I was under the assumption if we get value for 1 disk and multiply it by the number of disks in the disk array would get me the result for the disk array that is why I added an assumption of 1 disk. In general is there a formula for calculating availability of a disk array. Thank You
  2. Hi, I'm new to this thus I'm trying to understand about calculating Disk Array Availability (DAA). What I have understood so far is that availability is always 1, and Failure = 1÷MTBF. Could someone explain in simple English how to calculate DAA. Assuming I have 1TB and the time is 5 years, and the disk's MTBF is 1.6 millions hours (got this from Dell's website for a 15K RPM disk), I need to know the availability of this disk in 5 years, how do I calculate, what is the formula, I'm seeing , MTTl, MTTR, and MTTDL and getting confused. Another confusion is, is disk array availability associated only with RAID. Appreciate the assistance. Currently I'm using this as reference : http://www.ecs.umass.edu/ece/koren/architecture/Raid/reliability.html Also in the reference it says double disk failure, does the double disk mean any 2 disks or what, because once we find the availability of 1 disk would multiplying that into 2 NOT give us the double disk failure.. If anyone knows of any other good reference that explains in simple English. Thank You