Messages in this thread | | | From | "Mudama, Eric" <> | Subject | RE: Blockbusting news, results get worse | Date | Wed, 29 Oct 2003 13:11:27 -0700 |
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> -----Original Message----- > From: Pavel Machek [mailto:pavel@ucw.cz] > > > > If you don't FLUSH CACHE, you have no guarantees your > data is on the > > > platter. > > > > I think that the idea that is floating around is to > deliberately ruin > > the formatting on part of the drive in order to simulate a > bad block. > > > > Operation of disk drives immediately after a power failiure has been > > discussed before, by the way: > > > > http://marc.theaimsgroup.com/?l=linux-kernel&m=100665153518652&w=2 > > Well, that looks like pure speculation. > > BTW I *do* believe that powerfail can make the sector bad. Imagine you > bump into bad sector during write, and need to reallocate... > > Pavel
Both the linked post and Pavel's point are correct.
In a modern drive, tolerances are so tight that your drive is constantly re-writing blocks it knows it didn't write very well. In a power-fail event, there's little to no time to reallocate or reattempt a write, and even less energy available to "fix" things that aren't within specification anymore (spin speed, etc) ... if we don't get the actuator to the latch, your drive probably won't spin again and you'll lose *all* your data, so that is our number 1 concern when the power fails.
"Performance" IDE drives these days ship with 8MB buffers, which compounds the problem even further if you're trying to get data on the media after power has been cut.
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