Subject: Re: Log area on-disk for the journal
To: None <tech-kern@NetBSD.org>
From: Cary G. Gray <Cary.G.Gray@wheaton.edu>
Date: 10/23/2006 07:32:19
On Mon, 23 Oct 2006, Michael van Elst wrote:
>> Why? If you are up-to-date enough to have a journaled file system, why=20
>> don't you have up-to-date tools?
> You may need to transport the disk to an older system and you
> may want to run the same filesystem without journaling.
> This is not a necessary feature, it is just nice to have. With
> ext3 I can promote/demote from/to ext2 easily. With Solaris UFS
> the journal ist just a mount option.
>> Old tools don't know how to tell if a journal is dirty.
The downgrade from journaled to plain-old-ffs is something that should be
done by a tool on a not-currently-mounted filesystem. After checking that
the filesystem is in a clean state w.r.t. the journal, it can rewrite the
type flag in the superblock.