[ale] Ext4 adoption anyone?

[Michael B. Trausch]

On Wed, 21 Jan 2009 15:21:02 -0500
James Sumners <james.sumners at gmail.com> wrote:

> You might give [1] a read to see if the new features benefit your
> situation. I like the sound of improved performance, but I'm not sure
> if I would be willing to trade mounting and Ext3 partition as Ext2.
> That one feature is very handy if/when the need arises. It sounds to
> me like a pure Ext4 (created from scratch) filesystem cannot be
> mounted as a previous version.

The feature that blocks usage is extents.  You can convert back from
ext4 to ext3 simply by remounting the filesystem with extents disabled
and making a copy of any files that use extents, and then removing the
files that have extents and disabling that feature on the filesystem.

That said, I don't know that I'd need to do such a thing.  I suppose
this is probably because I tend to use custom kernels.  :-)  Even in
2.6.27 (the kernel that Ubuntu Intrepid uses) you can mount an ext4
filesystem as ext4dev, if you enable the flag on the filesystem that
says that it's okay for testing code to mount it.  I haven't had a
problem doing that on 2.6.27 as shipped and updated on Intrepid, but
it's been a little while since I've booted that kernel.

> One thing to be aware of if you decide to go Ext4 is this note from
> [1]:
> 
> "One very important thing to keep in mind is that __there is NOT Ext4
> GRUB support__. Well, that wasn't exactly true: There is grub support,
> but the grub versions used by your current distro don't support it.
> There's support in the GRUB2 development branch, but only from this
> commit and ahead. There are available grub2 packages in Ubuntu and
> debian-derived distros as the grub-pc package. In the 0.9x branch,
> there's not official support, but there's a Google SoC project that
> developed support for it, and Google finds patches. So choose
> yourself. The next release of distros based in Linux 2.6.28 will
> probably have support in one way or another. The safe option is to
> keep your /boot directory in a partition formatted with Ext3."

I traditionally use a very small ext2 partition for booting... I've
never seen the need for /boot to have a journal or any other special
features, since it's only ever updated when a new kernel is installed.
I usually mount /boot with the sync mount option, as well; not that big
a bother since the filesystem is only really used by the boot loader
and various utilities that are only run when updating the kernel.  Just
my two cents...

	--- Mike

-- 
My sigfile ran away and is on hiatus.
http://www.trausch.us/
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