[dm-devel] dm thin pool discarding

[Martin Wilck]

On Thu, 2019-01-10 at 12:52 +0100, Zdenek Kabelac wrote:
> Dne 10. 01. 19 v 12:40 Martin Wilck napsal(a):
> > 
>   > So far my understanding was that even without zeroing, an LVM
> thin
> > volume could be considered as a drive with "discard zeroes data"
> > property. If there's a flaw in the argument below, please point it
> > out
> > to me.
> > 
> 
> As said - if you discard 'less then aligned' chunk - nothing happens,
> so it cannot be takes as like it would be always zeroing...

Yuck, that's the Catch-22 then. Sorry for having missed that on the
first pass. Wouldn't it be wise to fail discard (or only zeroout?)
requests which aren't chunk-aligned, rather than just doing nothing? 

I for one would find it very attractive if dm-thin had a mode
supporting fast zeroout.

Martin