Re: Changing default "docker" storage to to Overlay2 in Fedora 26

Daniel J Walsh <dwalsh@xxxxxxxxxx> · Fri, 6 Jan 2017 15:29:51 -0500



    https://fedoraproject.org/wiki/Changes/DockerOverlay2

    
    On 01/06/2017 02:27 PM, Igor Gnatenko
      wrote:

    
      Shouldn't this be submitted as a change? 
        

        This would bring much more visibility to users
          of Fedora and even outside.

          
          -Igor
            Gnatenko
        
      
        On Jan 6, 2017 8:13 PM, "Daniel J
          Walsh" <dwalsh@xxxxxxxxxx>
          wrote:

          Upstream
            docker is moving to overlay2 by default for its storage.  We

            plan on following suit.  Their are some performance
            advantages of

            overlay2 over devicemapper in memory sharing, which we would
            like to

            take advantage of.   We now have SELinux support for
            Overlay  file

            systems, so the security should be just as good.

            
            Note: Overlay is not a Posix Compliant file system, so their
            could be

            problems with your containers running on overlay, so

            we want to make sure it is fairly easy to switch back to
            devicemapper.

            
            Devicemapper out of the box, on Fedora Workstation,
            currently defaults

            to loopback devices for storage, which has a performance
            penalty, but

            this was the only way we were able to get docker to work
            right away.

            Switching to overlay2 will cause the storage to be shared
            with / and

            will eliminate this performance overhead.   This is the way
            we will ship

            Fedora Workstation.

            
            On Fedora atomic host and Fedora server we have been storing

            devicemapper storage on a separate partition.  We plan on
            doing the same

            thing with overlay2.  This means separate device will be
            mounted on

            /var/lib/docker.  This will make it easier for someone to
            switch back to

            devicemapper, if overlay2 has problems.

            
            Upgraded systems will not be effected.

            
            If you want to switch from one storage to another take a
            look at the

            `atomic storage` commands.

            
            We will write up release notes to cover this change. Along
            with a blog

            explaining the commands to switch back and forth.

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