[lvm-devel] [PATCH]: Enable snapshots of mirrors

[Alasdair G Kergon]

On Thu, Oct 22, 2009 at 01:54:21PM -0500, Jon Brassow wrote:
> pv*:
> - commands ignored
 
pvmove is the only one to test I think and it ought to be OK, still 
refusing to let you manipulate any devices concerned.

> vgck:
> + seems to work, but I didn't try corrupting the VG

vgck already gives incorrect exit status anyway, someone pointed
out this week...
 
> vg*:
> - other vg commands/options ignored
 
I'd want to know that vgmerge and vgsplit always behave correctly and
understand the entire 'stack' of objects must remain together and give
sensible error messages/deal with name conflicts properly in the various
different cases.

> lvchange:
> + '-an' of mirror properly shuts down snapshots too
> + '-ay' of mirror properly starts up snapshots too
> + '-a[ny]' of snapshot gives proper error message
> + '--resync' of mirror origin properly resync's it
> - other options ignored

check permissions-handling too and --refresh and readahead setting
propagation.  
 
> lvdisplay:
> - largely ignored because I'm not familiar with normal output... but it
> seems fine

Well, simply, can you easily tell how things are set up from its output,
or does more descriptive text need to be added?
(E.g. instead of saying just 'snapshot', saying 'snapshot of mirror')
 

Most of this code was written with stacked devices in mind, but this is
the first time we'll actually be turning on and using these code paths.

Alasdair