On Tue, Apr 24, 2012 at 09:47:42AM +0200, Milan Broz wrote: > On 04/24/2012 08:45 AM, Yang Zhang wrote: > > I'm considering using ext4 on encrypted LVM (which uses LUKS and > > dm-crypt). Will the transactional guarantees in ext4's journaling be > > preserved? > > yes. dm-crypt operates in block layer, so it is filesystem responsibility > to properly set needed bits for IO (flush cache, FUA - force unit access) > and dmcrypt (device-mapper in general and block layer) must process them. > > (read http://lwn.net/Articles/400541/ for more info). > > In short, ext4, xfs, btrfs and similar filesystems supports > all features over dmcrypt. > > (Except very old kernels, but most of stable distros backports patches.) See also FAQ item 2.10, which I just have updated to reflect this information ;-) Arno > > Bonus: where may I find authoritative information on this (besides the source)? > The source is your best friend :-) > > basically this is the first commit introducing real barrier > (later replaced with FUA) support > http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=647c7db14ef9cacc4ccb3683e206b61f0de6dc2b > > You can also use blktrace to see how are fs requests propagated > to physical media. > > Milan > _______________________________________________ > dm-crypt mailing list > dm-crypt@xxxxxxxx > http://www.saout.de/mailman/listinfo/dm-crypt > -- Arno Wagner, Dr. sc. techn., Dipl. Inform., CISSP -- Email: arno@xxxxxxxxxxx GnuPG: ID: 1E25338F FP: 0C30 5782 9D93 F785 E79C 0296 797F 6B50 1E25 338F ---- One of the painful things about our time is that those who feel certainty are stupid, and those with any imagination and understanding are filled with doubt and indecision. -- Bertrand Russell _______________________________________________ dm-crypt mailing list dm-crypt@xxxxxxxx http://www.saout.de/mailman/listinfo/dm-crypt
