Difference is that ext3 is prepared to fall back to ext2 functionality when being read from a read-only device - which makes perfect sense, given that the journal's purpose is to protect the integrity of writes and (as Mark pointed out) it is of no value on a disk which will never again be written to.
ReiserFS, not recognizing that the journal is only relevant when it is possible to write to the disk, doesn't gracefully fall back to a journal-less version of itself the way ext3 does. As for ext2 vs ext3 for the read-only file system, there is a question of whether it's a disk which is to be written to once and then linked to and mounted read-only by everyone (in which case ext2 makes the most sense, with ext3 adding nothing but unnecessary overhead), or a disk which is regularly written to by one system - which you for some reason want be able to link to and mount read-only from another (in which case the ext3 journal does still serve a purpose while the disk is being accessed in write mode by that first system). On Wed, Aug 25, 2010 at 8:07 AM, Shane <[email protected]> wrote: > On Tue, 2010-08-24 at 11:00 -0400, Richard Troth wrote: > > > As others have said, ReiserFS wants to replay the journal. EXT3 does > > too. (Not sure about EXT4.) So for RO I recommend EXT2. > > Whilst I'm prepared to believe anything of reiserfs (not having > attempted to use it since before it was named thus), I query the > assertion re ext3. Were it to be mounted r/o everywhere, I fail to see > how the filesystem could have meta-data that would need replaying. > But I admit to not having specifically tested that - maybe someday. > > Shane ... > > ---------------------------------------------------------------------- > For LINUX-390 subscribe / signoff / archive access instructions, > send email to [email protected] with the message: INFO LINUX-390 or > visit > http://www.marist.edu/htbin/wlvindex?LINUX-390 > ---------------------------------------------------------------------- > For more information on Linux on System z, visit > http://wiki.linuxvm.org/ > ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390 ---------------------------------------------------------------------- For more information on Linux on System z, visit http://wiki.linuxvm.org/
