Anon wrote: > Hello, > > According to loop-AES.README section 2.2: > "Don't use a journaling file system on top of file backed loop device. [snip] With file backed > loop devices, correct write ordering may extend only to page cache (which resides in RAM) of > underlying file system. VM can write such pages to disk in any order it wishes, and thus break > write order expectation of journaling file system." > > What if I use the ReiserFS file system with the 2.6 kernel and the "nolog" mount option to disable > journaling as described at: > http://www.namesys.com/mount-options.html > > Could I then use ReiserFS on top of a file backed loop device? AFAIK/AFAICT this is a "should not" thing. You can use a journaling file-system-loopdevice on a journaling-files-system. I personally use a XFS-filesystem-in-loop on a reiserfs-partition because an XFS-filesystem can be easily grown. (unmount/losetup -d, grow the file, losetup/mount, xfs_growfs <mountpoint>, you are done. This way the loop-file stays the smallest possible size) BUT in case your computer breaks down while writing data the probability of a damaged filesystem increases enourmously as the blocks of the data and journal of the filesystem in the loop could be written to the disc-platter in any order. So the directorys (changed at the time of breakdown) and/or (especially) the journal (can be damaged/are plain garbage) with a much higher probability after a breakdown. IOW you practicaly "loose" the journaling feature (and this is exactly for the "error"-case. Most of the time the journal is "useless" as it's only use is for correcting errors after any kind of "mishap") and you SHOULD use a filesystem with a good fsck-tool. But appart from that i don't think there are any other problems. I remember some rants about possibel deadlocks if you stack journaling-filesystems and block-layers, but i say that a deadlocking filesystem is simply buggy. As long as you only read (with noatime) while breaking down or there aren't any dirty-buffers (and nothing unprocessed in the log) while breaking down,the filesystem shouldn't get any more damaged by a breakdown than any other filesystem directly on a block-device. So as long as your computer doesn't break down you shouldn't have any problems at all. :-) -- Real Programmers consider "what you see is what you get" to be just as bad a concept in Text Editors as it is in women. No, the Real Programmer wants a "you asked for it, you got it" text editor -- complicated, cryptic, powerful, unforgiving, dangerous. - Linux-crypto: cryptography in and on the Linux system Archive: http://mail.nl.linux.org/linux-crypto/
