Re: [linux-lvm] ReiserFS/XFS/JFS, LVM, Raid5

["Stephen C. Tweedie" <sct@redhat.com>]

Hi,

On Mon, Jul 03, 2000 at 06:16:27PM +0200, Andi Kleen wrote:
> On Mon, Jul 03, 2000 at 03:05:24PM +0100, Stephen C. Tweedie wrote:
> > The only known problem with journaling and software raid is to do with
> > the raid array rebuild code in raid1/5.  The rebuild could cause I/O
> > to be done in the wrong order for the filesystem, causing clean blocks
> > in the buffer cache to be flushed to disk as part of the rebuild.
> > That is fixed in the 2.4 soft raid.  raid0 and LVM were never affected
> > by this as they have no rebuild operation.
> 
> Note this applies only to the RAID1 in Raid 0.90 or in 2.4.
> Unpatched 2.2 does Raid1 reconstruction in user space only and should be 
> safe for journaling.

I think the user-space rebuild still has the same problem --- it
accesses the underlying raid device through the buffer cache, causing
clean buffers to be written to disk.  That's enough to kill
journaling.

Cheers,
 Stephen