On Tuesday 22 January 2002 15:07, Samuel Maftoul wrote:
> If user 1 had an ext2 disk, when user 2 umounts the filesystem with his
> disk plugged his filesystem got broken ( tested with ext2 and vfat).
> If user 1 had a vfat disk, then user 2 can cleanly umount the disk
> without breaking any filesystem.
In general, when you unmount a filesystem, the system caches and data
relevant for that filesystem are flushed to the disk. So if the first one
leaves withou unmounting his disk, he can even have a corrupted fs himself,
because some data didn't make it to the drive yet, there are just in caches.
When a second user comes and unmounts a disk, then the data are flushed (the
old data) and he gets a fs corruption, because the data were not from his
disk.
It is just matter of luck and it depends a lot on the buffering approach
chosen by the fs developers - ext2 tends to cache a lot of things to improve
performance and the disk flushes are not that frequent. If you manage to plug
your drive in a wrong moment, then you end up with a mess. You can easily
test this problem with floppies.
So, the solution is - teach your users to unmount disks before leaving, or
mount them in synchronous mode - but I am not sure, whether VFAT supports
that and it is a performance hog too.
Jan
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This archive was generated by hypermail 2b29 : Wed Jan 23 2002 - 21:00:54 EST