On Tue, 2003-08-12 at 13:39, Bruce Momjian wrote: > OK, I got some hard evidence. Here is a discussion on the Linux kernel > mailing list with postings from Allen Cox (ac Linux kernels) and Stephen > Tweedie (ext3 author). > > http://www.tux.org/hypermail/linux-kernel/1999week14/subject.html#start > > Search for "softupdates and ext2". > > Here is the original email in the thread: > > http://www.tux.org/hypermail/linux-kernel/1999week14/0498.html > > Summary is at: > > http://www.tux.org/hypermail/linux-kernel/1999week14/0571.html > > and conclusion in: > > http://www.tux.org/hypermail/linux-kernel/1999week14/0504.html > > I now remember the issue --- ext2 makes all disk changes asynchonously > (unless you mount it via sync, which is slow). This means that the file > system isn't always consistent on disk. > > UFS has always sync metadata (file/directory creation) to the disk so > the disk was always consistent, but doesn't sync the data to the disk, > for performance reasons. With soft updates, the metadata writes are > delayed, and written to disk in an order that keeps the file system > consistent. > > Is this enough evidence, or should I keep researching?
This is all 4 years old, though. Isn't that why the ext3 "layer" was created, and filesystems like reiserFS, XFS and (kinda) JFS were added to Linux? > --------------------------------------------------------------------------- > > Neil Conway wrote: > > On Tue, Aug 12, 2003 at 12:52:46AM -0400, Bruce Momjian wrote: > > I don't use Linux and was just repeating what I had heard from others, > > > and read in postings. I don't have any first-hand experience with ext2 > > > (except for a laptop I borrowed that wouldn't boot after being shut > > > off), but others on this mailing list have said the same thing. > > > > Right, and I understand the need to answer users asking about > > which filesystem to use, but I'd be cautious of bad-mouthing > > another OSS project without any hard evidence to back up our > > claim (of course if we have such evidence, then fine -- I > > just haven't seen it). It would be like $SOME_LARGE_OSS > > project saying "Don't use our project with PostgreSQL, as > > [EMAIL PROTECTED] had data corruption with PostgreSQL 6.3 on > > UnixWare" -- kind of annoying, right? > > > > > > (a) ext3 does metadata-only journalling by default > > > > > > If that is true, why was I told people have to mount their ext3 file > > > systems with metadata-only. Again, I have no experience myself, but why > > > are people telling me this? > > > > Perhaps they were suggesting that people mount ext2 using > > data=writeback, rather than the default of data=ordered. > > > > BTW, I've heard from a couple different people that using > > ext3 with data=journalled (i.e. enabling journalling of both > > data and metadata) actually makes PostgreSQL faster, as > > it means that ext3 can skip PostgreSQL's fsync request > > since ext3's log is flushed to disk already. I haven't > > tested this myself, however. > > > > -Neil -- +---------------------------------------------------------------+ | Ron Johnson, Jr. Home: [EMAIL PROTECTED] | | Jefferson, LA USA | | | | "Man, I'm pretty. Hoo Hah!" | | Johnny Bravo | +---------------------------------------------------------------+ ---------------------------(end of broadcast)--------------------------- TIP 7: don't forget to increase your free space map settings
