Messages in this thread | | | Date | Mon, 19 Mar 2001 16:08:57 -0500 | From | Jeremy Jackson <> | Subject | Re: Linux should better cope with power failure |
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Brian Gerst wrote:
> "Richard B. Johnson" wrote: > > > > On Mon, 19 Mar 2001, Otto Wyss wrote: > > > > > Lately I had an USB failure, leaving me without any access to my system > > > since I only use an USB-keyboard/-mouse. All I could do in that > > > situation was switching power off and on after a few minutes of > > > inactivity. From the impression I got during the following startup, I > > > assume Linux (2.4.2, EXT2-filesystem) is not very suited to any power > > > failiure or manually switching it off. Not even if there wasn't any > > > activity going on. > > > > > > Shouldn't a good system allways try to be on the save side? Shouldn't > > > Linux try to be more fail save? There is currently much work done in > > > getting high performance during high activity but it seems there is no > > > work done at all in getting a save system during low/no activity. I > > > think this is a major drawback and should be addressed as fast as > > > possible. Bringing a system to save state should allway have a high priority. > > > > > > How could this be accomplished: > > > 1. Flush any dirty cache pages as soon as possible. There may not be any > > > dirty cache after a certain amount of idle time. > > > 2. Keep open files in a state where it doesn't matter if they where > > > improperly closed (if possible). > > > 3. Swap may not contain anything which can't be discarded. Otherwise > > > swap has to be treated as ordinary disk space. > > > > > > These actions are not filesystem dependant. It might be that certain > > > filesystem cope better with power failiure than others but still it's > > > much better not to have errors instead to fix them. > > > > > > Don't we tell children never go close to any abyss or doesn't have > > > alpinist a saying "never go to the limits"? So why is this simple rule > > > always broken with computers? > > > > > > > Unix and other such variants have what's called a Virtual File System > > (VFS). The idea behind this is to keep as much recently-used file stuff > > in memory so that the system can be as fast as if you used a RAM disk > > instead of real physical (slow) hard disks. If you can't cope with this, > > use DOS. > > At the very least the disk should be consistent with memory. If the > dirty pages aren't written back to the disk (but not necessarily removed > from memory) after a reasonable idle period, then there is room for > improvement.
They are. If you leave your machine one for a minute or so (probably less is ok, but I don't know) the kernel will flush dirty buffers... fsck will complain, but the file's *data* blocks will be on the disk. There are way more reasons that this is a silly and annoying thread. You should read more about things like asynchronous/synchronous filesystems, lazy-write cacheing, etc, etc,. If you know how to write software and/or configure your system, you can avoid all of these problems. Or use a journaling filesystem ext3/xfs, etc. But I tire of this...
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