Date: Tue, 19 Apr 2016 17:04:47 -0700 From: "Jack L." <xxjack12xx@gmail.com> To: "freebsd-questions@freebsd.org" <freebsd-questions@freebsd.org> Cc: Valeri Galtsev <galtsev@kicp.uchicago.edu>, "Steve O'Hara-Smith" <steve@sohara.org> Subject: Re: Raid 1+0 Message-ID: <CALeGphzt0JQb=McEdniOT3Jz_OS-qFBJEnDahX8_cBTrYtUzfw@mail.gmail.com> In-Reply-To: <44a8kpcm14.fsf@be-well.ilk.org> References: <571533F4.8040406@bananmonarki.se> <57153E6B.6090200@gmail.com> <20160418210257.GB86917@neutralgood.org> <64031.128.135.52.6.1461017122.squirrel@cosmo.uchicago.edu> <20160419153824.7b679129f82a3cd0b18b9740@sohara.org> <40267.128.135.52.6.1461098148.squirrel@cosmo.uchicago.edu> <44a8kpcm14.fsf@be-well.ilk.org>
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On Tue, Apr 19, 2016 at 2:43 PM, Lowell Gilbert <freebsd-questions-local@be-well.ilk.org> wrote: > "Valeri Galtsev" <galtsev@kicp.uchicago.edu> writes: > >> On Tue, April 19, 2016 9:38 am, Steve O'Hara-Smith wrote: >>> On Mon, 18 Apr 2016 17:05:22 -0500 (CDT) >>> "Valeri Galtsev" <galtsev@kicp.uchicago.edu> wrote: >>> >>>> Not correct. First of all, in most of the cases, failure of each of the >>>> drives are independent events >>> >>> If only that were so. When the drives are as near identical as >>> manufacturing can make them and have had very similar histories they >>> can be expected to have very similar wear and be similarly close to >>> failure at all times, which makes it likely that the load imposed by >>> one failing will push another over. >> >> Sigh. You need suggest some physics that will make one drive affect >> another (aged or not aged doesn't matter for me). Then you will have me in >> your team. > > Correlation is not causation. > > It's not a big stretch to imagine that two nearly identical mechanical > devices, operated in nearly identical conditions, might wear out in a > nearly identical way at about the same time. There is no need for one > drive to affect the other. > > A fair number of people believe that this in fact occurs. I've looked > for evidence on the subject, and I haven't found anything (beyond > anecdotes) for or against the possibility. I think all hard drives are garbage and can die at any unpredictable time. Doesn't matter what brand, what model, what type, they all die unexpectedly. With that, I just make sure I have good backups just in case there's multiple drive failures in a raid set.
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