Re: RFC - new raid superblock layout for md driver

[Doug Ledford <dledford@redhat.com>]

On Thu, Nov 21, 2002 at 02:53:23PM -0600, Kevin Corry wrote:
> 
> LVM doesn't handle the filesystem resizing, the filesystem tools do. The only 
> thing you need is something in user-space to ensure the correct ordering. For 
> an expand, the MD device must be expanded first. When that is complete, 
> resizefs is called to expand the filesystem.
> 
> MD currently doesn't allow resize of RAID 0, 4 or 5, because expanding 
> striped devices is way ugly.

MD doesn't, raidreconf does but not online.

> If it was determined to be possible, the MD 
> driver may need additional support to allow online resize.

Yes, it would.  It's not impossible, just difficult.

> But it is just as 
> easy to add this support to MD rather than have to merge MD and DM.

Well, merging the two would actually be rather a simple task I think since 
you would still keep each md mode a separate module, the only difference 
might be some inter-communication call backs between LVM and MD, but even 
those aren't necessarily required.  The prime benefit I would see from 
making the two into one is being able to integrate all the disparate 
superblocks into a single superblock format that helps to avoid any 
possible startup errors between the different logical mapping levels.

-- 
  Doug Ledford <dledford@redhat.com>     919-754-3700 x44233
         Red Hat, Inc. 
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         Raleigh, NC 27606