[H-GEN] ext2 or ext3

[Anthony Towns]

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On Thu, Jun 20, 2002 at 09:42:02AM +1000, Jason Henry Parker wrote:
> > > I don't think journalling is necessarily useful in all situations, and
> > > in any event most journalled FSes only journal metadata, so I'm unsure
> > > of the utility.  Suggestions, anyone?
> Hmm, I think my real question here was `How does journalling save my
> ass in the face of disk corruption, is the hassle/benefit payoff
> better than, say, RAID?'  

Err, it doesn't: it saves your ass in the event of an unclean shutdown
from the OS point-of-view.

Various sorts of crashes:

	a) an application crashes, corrupting it's database
	b) the OS crashes, currupting any information not committed to the
		disk, whether user data or fs metadata
	c) a disk crashes, corrupting any information on that particular
		disk
	d) the disk subsystem or entire computer crashes, losing everything on
		every disk you have attached

RAID-1 or 5 will save you from (c), journalling will save you from some
or all of (b), attached backups (in /srv/backups, say) will save you from
(a), and unattached/off-site backups will save you from (a-d).

Robust applications will protect you from (a), a UPS and good choice of
kernel will protect you from (b), and buying reliable components will
protect you from (c,d).

There's also the possibility of active attacks, which are more likely to
focus on choice (b), randomly crashing the system (because it's so badly
DoSed you have to hit the reboot key) or choice (d), killing everything
on all your disks (rm -rf /, etc).

YMMV, the above may be fictional, and any resemblence to real disasters
may be purely coincidental.

Cheers,
aj

-- 
Anthony Towns <aj at humbug.org.au> <http://azure.humbug.org.au/~aj/>
I don't speak for anyone save myself. GPG signed mail preferred.

     ``BAM! Science triumphs again!'' 
                    -- http://www.angryflower.com/vegeta.gif

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