Rainer J.H. Brandt wrote: > Ronald, > > thanks for your comments. > > I was thinking about this scenario: > > Host w continuously has a UFS mounted with read/write access. > Host w writes to the file f/ff/fff. > Host w ceases to touch anything under f. > Three hours later, host r mounts the file system read-only, > reads f/ff/fff, and unmounts the file system. > > My assumption was: > > a1) This scenario won't hurt w, > a2) this scenario won't damage the data on the file system, > a3) this scenario won't hurt r, and > a4) the read operation will succeed, > > even if w continues with arbitrary I/O, except that it doesn't > touch anything under f until after r has unmounted the file system.
If the filesystem is mounted on host w, then host w is entitled to write to it at any time. If you want to reliably ensure that w does not perform any writes, then it must be unmounted on w. Note also that mounting a filesystem read-only does not guarantee that the disk will not be written, because of atime updates (this is arguably a Unix design flaw, but still has to be taken into account). So r may also write to the disk, unless the filesystem is specifically mounted with options that prevent any physical writes. > Of course everything that you and Tim and Casper said is true, > but I'm still inclined to try that scenario. I don't understand why you would ever want to risk this with valuable data. -- David Hopwood <[EMAIL PROTECTED]> _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
