On 2014-01-09 13:08, Chris Murphy wrote: > > On Jan 9, 2014, at 5:41 AM, Duncan <1i5t5.dun...@cox.net> wrote: >> Having checksumming is good, and a second >> copy in case one fails the checksum is nice, but what if they BOTH do? >> I'd love to have the choice of (at least) three-way-mirroring, as for me >> that seems the best practical hassle/cost vs. risk balance I could get, >> but it's not yet possible. =:^( > > I'm on the fence on n-way. > > HDDs get bigger at a faster rate than their performance improves, so rebuild > times keep getting higher. For cases where the data is really important, > backup-restore doesn't provide the necessary uptime, and minimum single drive > performance is needed, it can make sense to want three copies. > > But what's the probability of both drives in a mirrored raid set dying, > compared to something else in the storage stack dying? I think at 3 copies, > you've got other risks that the 3rd copy doesn't manage, like a power supply, > controller card, or logic board dying. > The risk isn't as much both drives dying at the same time as one dying during a rebuild of the array, which is more and more likely as drives get bigger and bigger.
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