[ale] initramfs capable of a multi-device btrfs / new initramfs with dracut help?

[Greg Freemyer]

On Fri, Jul 16, 2010 at 12:49 PM, Michael B. Trausch <mike at trausch.us> wrote:
> On Fri, 2010-07-16 at 11:34 -0400, Brian W. Neu wrote:
>> btrfs has RAID levels 0,1,10 built-in (and will have 5 & 6 some day in
>> the probably far-off distant future)
>>
>> I don't want to use mdraid because not only is it unnecessary but it
>> prevents checksums from being able to identify a faulty drive.  mdraid
>> really offers no integrity checking, which I'm not willing to do
>> without anymore.
>
> If btrfs is seriously trying to give ZFS a run for its money, it's going
> to adopt RAID5/6 and ZFS's non-standard RAID-Z, and hopefully sooner
> rather than later.  I am also anxiously awaiting the data deduplication
> feature, when it arrives.
>
> However, it's going to be a while before I really trust btrfs.
> Development on it has slowed way down, it would appear, which stinks.  I
> love the speed of the FS, and I love the fact that it can dynamically
> grow and shrink.  I like the whole notion of copy-on-write snapshots at
> the file level, because that makes experimenting with very large files
> like virtual machine images quite easy to do in an efficient manner
> without having application-level support for stacking images.

There are ext3 patches for snapshots too.

http://next3.sourceforge.net/

ext3 is not really accepting big patches like that, so they will
likely never get in mainline.

In theory they are working on getting a set of ext4 patches going.
Lots of differences between ext3 and ext4 at that level in the source,
so who knows if and when it will happen.

If curious Amir G. <amir73il at users.sourceforge.net> has been the main
person posting to the ext4 list IIRC.

> It would be nice, though, if I could get rid of the mdraid setup that I
> have currently.  I really am finding that I hate Linux's software RAID.
> I have been trying for weeks to make it act intelligently, but it
> doesn't seem to be really capable of that without lots of manual help.
> I'm probably missing something (and honestly, I *seriously* hope that I
> am) but as it is, I cannot reboot my server running the RAID without
> physically being there to bring up the RAID.  That's not cool.  I had to
> disable the automatic feature because it would always assemble the RAID
> improperly and force a three-day rebuild process, which is even less
> acceptable IMHO.

The mdraid mailing list is very responsive to end user queries about usage etc.

I'd post a question there.  "Linux RAID" <linux-raid at vger.kernel.org>,

Remember in the LKML lists you don't have to subscribe to post.  And
default behavior is to reply-all, so you'll be part of the thread as
long as it lasts.

> To be able to replace that with a filesystem that can intelligently
> rebuild only the necessary data when a drive fails?  That would be a
> delight!
>
>        --- Mike

Greg