[dm-devel] DM_snapshot_cow filesystem (dmsetup create snapshot)

[Alasdair G Kergon]

On Wed, Nov 30, 2011 at 05:34:25PM -0600, Douglas McClendon wrote:
> So wouldn't it be much better as far as the user is concerned if, the  
> instant a snapshot reached capacity, it fell over into a read-only state  
> (instead of being marked invalid?), such that further corruption beyond  

That would mean your *origin* device becoming read-only as well.

It's been discussed before.  Nobody has been motivated to write the code,
as there's no need for it on a properly-managed system.

If you care enough about your snapshot contents, then surely you
would be monitoring it to make sure it doesn't fill up - and if you're
going to run out of space and can't expand, you would shut down your system
yourself in a *controlled* way *before* running out of space!

Alasdair