Re: 2.6.19-rc1-mm1

[Theodore Tso <tytso@mit.edu>]

On Tue, Oct 10, 2006 at 12:09:28AM -0700, Andrew Morton wrote:
> 
> - Added the ext4 filesystem.  Quick usage instructions:
> 
>   - Grab updated e2fsprogs from
>     ftp://ftp.kernel.org/pub/linux/kernel/people/tytso/e2fsprogs-interim/
> 
>   - It's still mke2fs -j /dev/hda1
> 
>   - mount /dev/hda1 /wherever -t ext4dev
> 
>   - To enable extents,
> 
> 	mount /dev/hda1 /wherever -t ext4dev -o extents

Looks like you didn't take the updated patch from Shaggy which
requires that you use tune2fs -O extents first?  (This requires the
e2fsprogs-interim patches.)

The plan is that mount -o extents is not going to be the long-term way
that extents will be enabled.  I can imagine a -o noextents option,
which might be used with remount to do an on-line rollback from
extents to non-extents, but normally you shouldn't need to use a mount
option to enable a feature that are filesystem format-related.  Those
should be implied by the appropriate flags in the superblock.

Mount -o nobh is a different story, since that's just a implementation
detail --- although for ext4, maybe we should just make nobh a
default, since that way more people will test it and hopefully,
eventually nobh will be the only way of doing things, right?

>     Making the journal larger than the mke2fs default often helps
>     performance with metadata-intensive workloads.

The default was increased significantly in e2fsprogs 1.40; if someone
who has their favorite metadata-intesive benchmark could test and see
if we should be using even larger defaults for certain "mke2fs -T 
<workload-type>" configurations, I'd really appreciate it.

					- Ted