Re: [atomic-devel] Fedora 26 change: using overlayfs as default

[Vivek Goyal <vgoyal redhat com>]

On Fri, Jan 06, 2017 at 01:38:09PM -0800, Josh Berkus wrote:
> On 01/06/2017 11:24 AM, Vivek Goyal wrote:
> > On Thu, Jan 05, 2017 at 04:16:45PM -0800, Josh Berkus wrote:
> >> So, I've done some testing, thanks to Dusty's setup.
> >>
> >> I wasn't able to test on Kubernetes because of some setup issues.
> >> However, I hammered away at Docker using some IO-intensive applications,
> >> including PostgreSQL and Etcd, both of which write data frequently to
> >> some unexpected places.
> >>
> >> So far I haven't seen any unexpected IO errors from containers running
> >> under overlayfs.
> >>
> >> And having all of storage be one big volume is really nice; it
> >> eliminates a longstanding issue we've had with disk allocation; the
> >> whole disk is simply available.
> >>
> >> So +1 on moving to overlayfs for F26.
> > 
> > Nice to hear that Josh. BTW, on fedora server and atomic, overlay storage
> > will still come from non-root fs partition. That will allow one to switch
> > back to devicemapper if overlay2 does not work for them.
> 
> Why?  It didn't when I just ran the test.  Why can't we have a shared
> partition?

We can have depending on what's the default configuration of storage. So
for atomic-host, rootfs was 3G by default and rest of the space was free
which used to be used by devicemapper.

I think you are talking of some other image where default rootfs
configuration looks different. If rootfs is consuming all space available
on disk by default, then shared partition makes perfect sense.

So whether to have shared partition by default or setup a separate logical
volume to store images/containers depends on default storage setup of
image.

Vivek
> 
> -- 
> --
> Josh Berkus
> Project Atomic
> Red Hat OSAS