[Gluster-devel] Release 3.10 feature proposal : Volume expansion on tiered volumes.

[Hari Gowtham]

I have answered the questions inline.

----- Original Message -----
> From: "Shyam" <srangana at redhat.com>
> To: "Hari Gowtham" <hgowtham at redhat.com>, "gluster-devel" <gluster-devel at gluster.org>
> Sent: Thursday, December 8, 2016 6:05:27 PM
> Subject: Re: [Gluster-devel] Release 3.10 feature proposal : Volume expansion on tiered volumes.
> 
> Hi Hari,
> 
> Thanks for posting this issue to be considered part of 3.10.
> 
> I have a few questions inline.
> 
> Shyam
> 
> On 12/08/2016 01:23 AM, Hari Gowtham wrote:
> > Hi,
> >
> > To support add/remove brick on tiered volumes we are planing to separate
> > the tier into a separate process in the service framework and add the
> > add/remove brick support. Later the users will be able to spawn rebalance
> > on tiered volumes (which is not possible).
> 
> I assume tier as a separate process is from the rebalance deamon
> perspective, right? Or, is it about separating the xlator cod efrom DHT?

Yes. it is from the rebalance Daemon perspective. 

> 
> Also, Dan would like your comments as Tier maintainer, on the maturity
> of the below proposal for 3.10 inclusion? Could you also add the
> required labels [2] to the issue as you see fit, and if this passes your
> inspection, then let us know and I can mark it for 3.10 milestone in github.
> 
> >
> > The following are the steps planed to be performed:
> >
> > *) tier as a service (final stages of code review)
> 
> Can we get links to the code, and also the design spec if available, for
> the above (and possibly as a whole)

Links to code: 
tier as a service : http://review.gluster.org/#/c/13365/45
separation of attach tier from add-brick : http://review.gluster.org/#/c/15503/10
add brick on a tiered volume : http://review.gluster.org/#/c/15740/

design spec:
http://review.gluster.org/#/c/15519/2

> 
> > *) we are separating the attach tier from add brick and detach from
> >    remove brick.
> > *) infra to support add/remove brick.
> > *) rebalance process on a tiered volume.
> > *) a few patches to take care of the issues that will be arising
> >    eg: while adding a brick on a tiered volume, the tier process has to
> >    be stopped as the graph switch occurs. and other issues like this.
> >
> > The whole volume expansion will be in an experimental state. while the
> > separation of tier into a separate service framework and attach/detach
> > tier separation from add/remove brick should be back to stable state before
> > the release of 3.10
> 
> What is the mitigation plan in case this does not get stable? Would you
> have all commits in ready but not merged state till it is stable?
The changes that make the code easier to maintain, like the tier as service,
attach/detach tier separation from add/remove brick are fine to be merged.
Regarding the add/remove brick on tiered volumes and spawning rebalance on it
will be on gerrit till they become stable.
  
> 
> This looks like a big change, and also something that has been going on
> for some time now, based on your comments above.
Yes it is.
> 
> >
> > [1] https://github.com/gluster/glusterfs/issues/54
> [2] https://github.com/gluster/glusterfs/labels
> 

-- 
Regards, 
Hari.