[Gluster-users] Request for Comments: Upgrades from 3.x to 4.0+

[Amudhan P]

if doing an upgrade from 3.10.1 to 4.0 or 4.1, will I be able to access
volume without any challenge?

I am asking this because 4.0 comes with DHT2?




On Thu, Nov 2, 2017 at 2:26 PM, Kaushal M <kshlmster at gmail.com> wrote:

> We're fast approaching the time for Gluster-4.0. And we would like to
> set out the expected upgrade strategy and try to polish it to be as
> user friendly as possible.
>
> We're getting this out here now, because there was quite a bit of
> concern and confusion regarding the upgrades between 3.x and 4.0+.
>
> ---
> ## Background
>
> Gluster-4.0 will bring a newer management daemon, GlusterD-2.0 (GD2),
> which is backwards incompatible with the GlusterD (GD1) in
> GlusterFS-3.1+.  As a hybrid cluster of GD1 and GD2 cannot be
> established, rolling upgrades are not possible. This meant that
> upgrades from 3.x to 4.0 would require a volume downtime and possible
> client downtime.
>
> This was a cause of concern among many during the recently concluded
> Gluster Summit 2017.
>
> We would like to keep pains experienced by our users to a minimum, so
> we are trying to develop an upgrade strategy that avoids downtime as
> much as possible.
>
> ## (Expected) Upgrade strategy from 3.x to 4.0
>
> Gluster-4.0 will ship with both GD1 and GD2.
> For fresh installations, only GD2 will be installed and available by
> default.
> For existing installations (upgrades) GD1 will be installed and run by
> default. GD2 will also be installed simultaneously, but will not run
> automatically.
>
> GD1 will allow rolling upgrades, and allow properly setup Gluster
> volumes to be upgraded to 4.0 binaries, without downtime.
>
> Once the full pool is upgraded, and all bricks and other daemons are
> running 4.0 binaries, migration to GD2 can happen.
>
> To migrate to GD2, all GD1 processes in the cluster need to be killed,
> and GD2 started instead.
> GD2 will not automatically form a cluster. A migration script will be
> provided, which will form a new GD2 cluster from the existing GD1
> cluster information, and migrate volume information from GD1 into GD2.
>
> Once migration is complete, GD2 will pick up the running brick and
> other daemon processes and continue. This will only be possible if the
> rolling upgrade with GD1 happened successfully and all the processes
> are running with 4.0 binaries.
>
> During the whole migration process, the volume would still be online
> for existing clients, who can still continue to work. New clients will
> not be possible during this time.
>
> After migration, existing clients will connect back to GD2 for
> updates. GD2 listens on the same port as GD1 and provides the required
> SunRPC programs.
>
> Once migrated to GD2, rolling upgrades to newer GD2 and Gluster
> versions. without volume downtime, will be possible.
>
> ### FAQ and additional info
>
> #### Both GD1 and GD2? What?
>
> While both GD1 and GD2 will be shipped, the GD1 shipped will
> essentially be the GD1 from the last 3.x series. It will not support
> any of the newer storage or management features being planned for 4.0.
> All new features will only be available from GD2.
>
> #### How long will GD1 be shipped/maintained for?
>
> We plan to maintain GD1 in the 4.x series for at least a couple of
> releases, at least 1 LTM release. Current plan is to maintain it till
> 4.2. Beyond 4.2, users will need to first upgrade from 3.x to 4.2, and
> then upgrade to newer releases.
>
> #### Migration script
>
> The GD1 to GD2 migration script and the required features in GD2 are
> being planned only for 4.1. This would technically mean most users
> will only be able to migrate from 3.x to 4.1. But users can still
> migrate from 3.x to 4.0 with GD1 and get many bug fixes and
> improvements. They would only be missing any new features. Users who
> live on the edge, should be able to the migration manually in 4.0.
>
> ---
>
> Please note that the document above gives the expected upgrade
> strategy, and is not final, nor complete. More details will be added
> and steps will be expanded upon, as we move forward.
>
> To move forward, we need your participation. Please reply to this
> thread with any comments you have. We will try to answer and solve any
> questions or concerns. If there a good new ideas/suggestions, they
> will be integrated. If you just like it as is, let us know any way.
>
> Thanks.
>
> Kaushal and Gluster Developers.
> _______________________________________________
> Gluster-users mailing list
> Gluster-users at gluster.org
> http://lists.gluster.org/mailman/listinfo/gluster-users
>
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