[Gluster-devel] expanding tiered volumes

Vijay Bellur vbellur at redhat.com
Mon Feb 23 10:26:58 UTC 2015

On 02/16/2015 08:20 PM, Dan Lambright wrote:

> One of the hard parts has been integrating this new volume type with existing features, such as adding and removing bricks.
> Allowing the user to add and remove bricks to both the hot and cold tiers is a challenge on multiple levels.
> The CLI commands would have to specify which tier to add/remove bricks to.

Could you please detail the CLI being considered for defining a hot/cold 
tier? I think that will be useful in understanding the problem better.

> New phenomena could occur such as rebalancing operations happening simultanously on both the hot and cold tiers.
> In general rebalancing at the same time cache promotion/demotion is happening is a tricky problem, it requires some tweaks to DHT which are forthcoming.
> To manage the complexity and get this feature done "on time" (per Gluster's release schedule) we would like to only allow adding and removing bricks to the cold
> tier for the first version. I would like to see if there are any comments from the upstream community.

We can have some flexibility if the core feature lands by end of this 
week. Are there any thoughts on how either tier can be expanded or 
shrunk? If it is not very intrusive and seems appropriate to be pulled 
in as part of a bug fix, we can look at this beyond feature freeze and 
before code freeze.


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