On Sat, Apr 13, 2013 at 1:17 PM, Steven D'Aprano <steve+comp.lang.pyt...@pearwood.info> wrote: > On Sat, 13 Apr 2013 03:33:29 +0100, Nobody wrote: >> If you want to wait for the data written to be written to the physical >> disk (in order to obtain specific behaviour with respect to an unclean >> shutdown), use f.flush() followed by os.fsync(f.fileno()). > > If only it were that simple. It has been documented that some disks will > lie, even when told to sync. When I say "some", I mean *most*. There's > probably nothing you can do about it, apart from not using that model or > brand of disk, so you have to just live with the risk.
It's often close to that simple. With most hard disks, you can make them 100% reliable, but you may have to check some disk parameters (on Linux, that's just a matter of writing to something in /proc somewhere, don't remember the details but it's easy to check). The worst offenders I've met are SSDs... > USB sticks are especially nasty. I've got quite a few USB thumb drives > where the "write" light keeps flickering for anything up to five minutes > after the OS reports that the drive has been unmounted and is safe to > unplug. I corrupted the data on these quite a few times until I noticed > the light. And let's not even mention the drives that have no light at > all... ... but you've met worse. > But my favourite example of lying hard drives of all time is this: > > http://blog.jitbit.com/2011/04/chinese-magic-drive.html > > I want one of those! Awesome! It's the new version of DoubleSpace / DriveSpace! http://en.wikipedia.org/wiki/DriveSpace (And its problems, according to that Wikipedia article, actually had the same root cause - write caching that the user wasn't aware of. Great.) ChrisA -- http://mail.python.org/mailman/listinfo/python-list
