On Wed, Mar 10, 2021 at 7:53 PM Dan Williams <dan.j.williams(a)intel.com> wrote:
On Wed, Mar 10, 2021 at 6:27 AM Matthew Wilcox <willy(a)infradead.org> wrote:
> On Wed, Mar 10, 2021 at 08:21:59AM -0600, Goldwyn Rodrigues wrote:
> > On 13:02 10/03, Matthew Wilcox wrote:
> > > On Wed, Mar 10, 2021 at 07:30:41AM -0500, Neal Gompa wrote:
> > > > Forgive my ignorance, but is there a reason why this isn't wired
> > > > Btrfs at the same time? It seems weird to me that adding a feature
> > >
> > > btrfs doesn't support DAX. only ext2, ext4, XFS and FUSE have DAX
> > >
> > > If you think about it, btrfs and DAX are diametrically opposite things.
> > > DAX is about giving raw access to the hardware. btrfs is about offering
> > > extra value (RAID, checksums, ...), none of which can be done if the
> > > filesystem isn't in the read/write path.
> > >
> > > That's why there's no DAX support in btrfs. If you want DAX, you
> > > to give up all the features you like in btrfs. So you may as well use
> > > a different filesystem.
> > DAX on btrfs has been attempted. Of course, we could not
> But why? A completeness fetish? I don't understand why you decided
> to do this work.
Isn't DAX useful for pagecache minimization on read even if it is
awkward for a copy-on-write fs?
Seems it would be a useful case to have COW'd VM images on BTRFS that
don't need superfluous page cache allocations.
I could also see this being useful for databases (and maybe even swap
files!) on Btrfs, if I'm understanding this feature correctly.
真実はいつも一つ！/ Always, there's only one truth!