Re: Transactions

On Tue, Dec 05, 2000 at 06:15:28PM +0100, Helge Bahmann wrote:
> On Tue, 5 Dec 2000, Mike Castle wrote:
>
> > On Tue, Dec 05, 2000 at 04:25:20PM +0100, Helge Bahmann wrote:
> > > You will still experience data loss if you do not use a journalling
> > > filesystem; get the ext3 patches or try reiserfs.
> >
> > I believe this statement is wrong.
> >
> > fsync should force all data to disk. Period. Regardless of using ext2,
> > ext3, or reiserfs.
> yes, if fsync completes, the data is on disk; but if you hard-reset the
> system (as indicated in the original mail) while fsync is in progress you
> will likely end up with a garbled filesystem

Look at 'softupdates' as implemented in FreeBSD.
In a nutshell, this does all disk writes as 'transactions',
which are either committed or rolled back if the system
hangs during an update.

fsck after a reboot becomes unnecessary
(6 powerfails so far, fsck never found anything needing fixing).
But all this just protects filesystme integrity, it can't recreate data.
Don't think ext3 would help;

If you power down a box, expect to shag the disk
(without something like softupdates).
UPS might be an idea if it's a concern.

--
Rasputin
Jack of All Trades :: Master of Nuns