Question on migrating data between PVs in xfs

[Wei Lin]

On 16-08-11 07:51:49, Dave Chinner wrote:
> On Wed, Aug 10, 2016 at 06:31:32PM +0200, Emmanuel Florac wrote:
> > Le Wed, 10 Aug 2016 20:56:39 +1000
> > Dave Chinner <david at fromorbit.com> écrivait:
> > 
> > > Have you lookd at using dm-cache instead of modifying the
> > > filesystem?
> > > 
> > 
> > Or bcache, fcache, or EnhanceIO. So far from my own testing bcache is
> > significantly faster and dm-cache by far the slowest of the bunch, but
> > bcache needs some more loving (his main developer is busy writing
> > some new tiered, caching filesystem instead).
> 
> Yeah, the problem with bcache is that it is effectively an orphaned
> driver. If there are obvious and reproducable performance
> differentials between bcache and dm-cache, you should bring them to
> the attention of the dm developers to see if they can fix them...
> 
> Cheers,
> 
> Dave.
> -- 
> Dave Chinner
> david at fromorbit.com

Software like dm-cache and bcache seem to use SSDs merely as caches
instead of aggregating the capacity of all devices. However I just found
aufs and overlayfs, which conceptually suit the purpose better.

Cheers,
-- 
Wei Lin