[Gluster-devel] metdata-volume for gluster

[Jeff Darcy]

> In gluster 3.7 multiple features (Snapshot scheduler, NFS Ganesha, Geo-rep)
> are planning to use
> additional volume to store metadata related to these features. This volume
> needs to be manually
> created and explicitly managed by an admin.
> 
> I think creating and managing these many metadata volume would be an overhead
> for an admin. Instead
> of that I am proposing to have a single unified metata-volume which can be
> used by all these features.
> 
> For simplicity and easier management we are proposing to have a pre-defined
> volume name.
> If needed this name can be configured using a global gluster option.
> 
> Please let me know if you have any suggestions or comments.

Do these metadata volumes already exist, or are they being added to designs
as we speak?  There seem to be a lot of unanswered questions that suggest
the latter.  For example...

* What replication level(s) do we need?  What "performance" translators
  should be left out to ensure consistency?

* How much storage will we need?  How will it be provisioned and tracked?

* What nodes would this volume be hosted on?  Does the user have to
  (or get to) decide, or do we decide automatically?  What happens as
  the cluster grows or shrinks?

* How are the necessary daemons managed?  From glusterd?  What if we
  want glusterd itself to use this facility?

* Will there be an API, so the implementation can be changed to be
  compatible with similar facilities already scoped out for 4.0?

I like the idea of this being shared infrastructure.  It would also be
nice if it can be done with a minimum of administrative overhead.  To
do that, though, I think we need a more detailed exploration of the
problem(s) we're trying to solve and of the possible solutions.