[Vdo-devel] [BUG] Discard not working

[Michael Niewöhner]

On Wed, 2018-08-08 at 22:09 +0200, Gionatan Danti wrote:
> Il 08-08-2018 17:35 Michael Niewöhner ha scritto:
> > Hi Bryan,
> > 
> > ah, thanks... I didn't realize that.
> > What is the reason for not passing down discard like ext*, LVM, ZFS, 
> > ... ?
> > Using VDO on a SSD would be very bad.
> > 
> > IMHO at least there should be an option to enable discard when needed.
> > In my case having discard is an absolute must-have because of ZFS.
> > Not having discard would mean ZFS never knows which blocks are unmapped 
> > and
> > don't need to be synced/scrubbed/...
> > (I don't want to use ZFS deduplication because of the memory 
> > requirements.)
> > 
> > Best regards
> > Michael
> 
> Hi, before going full-on for data deduplication, I would advice you to 
> test if your data *are actually deduplicable*.
> I evaluated both ZFS and VDO dedup and found that, for my VMs, they 
> provided minimal benefit over plain ZFS LZ4 compression at a very big 
> performance hit.
> 
> So, if your data are deduplicable - go ahead. If not, please stop here 
> and simply use compression.
> 
> Regards.


Hi,

since all my VMs are Linux VMs with exactly the same base, I am sure it is
deduplicable.
Thanks anyway.

Best regards
Michael