Re: Status of ReiserFS + Journalling

[Daniel Phillips]

Andi Kleen wrote:
> On Wed, Oct 04, 2000 at 01:42:46AM -0600, Andreas Dilger wrote:
> > You should ask the reiserfs mailing list for outstanding problems.  As
> > far as LVM is concerned, I don't think there is a problem, but watch out
> > for software RAID 5 and journalling filesystems (reiser or ext3, at least
> > under 2.2) - it can have problems if there is a disk crash.
> 
> It is not inherent to journaling file systems, linux software raid  5
> can always corrupt your data when you have a system crash with a disk
> crash (no way to write stripe sets atomically and half writen strip sets
> usually give random data for any crashed block in it when xored against parity)

'Atomic' - a word that makes my ears perk up.  Tux2 is all about atomic
updating.  Could you please give a simple statement of the problem for a
person who doesn't know much more about RAID than that it stands for
Redundant Array of Inexpensive Disks (Drives?)

Given a clear statement of the problem, I think I can show how to update
the stripes atomically.  At the very least, I'll know what interface
Tux2 needs from RAID in order to guarantee an atomic update.

> In this case "safe" just means that you don't need a fsck to be sure that
> the metadata is consistent -- data is never guaranteed to be consistent
> unless you have applications that use fsync/O_SYNC properly (=basically do
> their own journaling)

I truly believe that's a temporary situation.

> So overall I would not be worried too much, it isn't much worse with a
> journaled fs than it is without it.

But if it could be better...

--
Daniel