On Sun, 04 Oct 2009 21:53:11 +0200 Rodolphe Rocca <[email protected]> wrote: > > or if you don't cleanly power off your computer after > > unmounting a filesystem, things will break. > > but not this one. > > AFAIK when a fs is unmounted, a sync happens on the virtual device and > the unmount operation is blocking until all data has been flushed to > the disk (write cache). After what it's up to the hard drive firmware > to flush the write cache if it is enabled. So normally when unmount > returns, data is at least in the write cache of the drive. A power off > during the internal write cache flushing process will trigger data > loss. Not sure if the reboot will too.
Unmounting a filesystem doesn't force the disk to really really write its contents properly. In the general case, there's absolutely nothing a computer can do to force data to be really really written, whatever that even means. > Concerning the merged files I agree that not much more can be done to > make paludis more resilient to a system crash. > > But what about /var/cache/db ? Assuming you mean /var/db/pkg... > What I'm thinking about is letting paludis work as much as possible > in a temporary vdb directory and rename this directory in the safest > possible way once everything is done. No point. > Next time paludis runs, it could be able to detect inconsistencies and > automatically fix them. Something like : A full VDB scan is slooooow, and might require permissions Paludis doesn't currently have. That's really not something we want to do. > Would it be insane ? Yes, it would. First, there is absolutely nothing whatsoever that userland software can do to deal with the user randomly powering off their computer. Second, this is a huge amount of effort to avoid something that is entirely caused by a particularly unpleasant case of user error. -- Ciaran McCreesh
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