Nesting gvinum?

[Ulf Lilleengen]

On Wed, May 09, 2007 at 11:22:11AM -0500, Jonathan Dobbie wrote:
> Rick C. Petty wrote:
> > On Wed, May 09, 2007 at 09:43:14AM -0500, Jonathan Dobbie wrote:
> >   
> >> I was hoping to have something like md+LVM where I could change the size
> >> of RAID 5 volumes.  Could I have a large gvinum raid-5 volume and then
> >> make 3 gvinum volumes on top that could be resized?
> >>     
> >
> > Except for the nesting, this is precisely what gvinum does.  Why do you
> > need nesting?  Resizing volumes is something gvinum is supposed to be able
> > to do.
> >
> >   
> I thought that it could only resize striped volumes?  Would you happen
> to have a guide handy?  If I, say, wanted to resize usr and log to add
> 20GB to log, could I drop the s0 subdisk from both, resize, readd, sync
> and then repeat for s1 and s2?

You can only make them bigger. I wouldn't bet on it to work for raid5 in gvinum,
but it should work for simple plex organisations, although I really need to test
this better to find out what works and don't. But making gvinum handle this
properly is one of my goals this summer.

To grow the volume, you can add new subdisks to gvinum, and the plex and volume
of that uses that subdisk will be larger. However, you need to run growfs to
grow the _filesystem_ on top of it.

To shrink gvinum volumes is not possible, but shouldn't be that difficult to
implement in gvinum for the simplest plex organisations. However, you need to
be able to shrink UFS, and that is not supported.

If you're looking for another fs, you might want to try ZFS, but remember that
it is quite experimental compared to UFS.

There are some guides on gvinum out there that isn't completely outdated, and
google are able to find most of them. The handbook also gives a more general
guide to gvinum and vinum.

-- 
Ulf Lilleengen