Bug 765037 (GLUSTER-3305)

Summary: enable changing of volume type after its creation
Product: [Community] GlusterFS Reporter: Amar Tumballi <amarts>
Component: glusterdAssignee: Amar Tumballi <amarts>
Status: CLOSED CURRENTRELEASE QA Contact:
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Priority: medium    
Version: mainlineCC: gluster-bugs, lasse.borchard, vraman
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Hardware: x86_64   
OS: Linux   
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Description Amar Tumballi 2011-08-02 07:26:42 UTC 
ie, if volume is created with plain distribute, and user want to make it a 'replciate' type volume with 2 copies. 

Or if a volume has replica 2 as the setup, enable it to change to 'replica 3' during run time.

same with stripe.

also enable reducing the replica count.
Comment 1 Amar Tumballi 2011-09-06 03:01:09 UTC 
Just for future reference:

Anand Avati: writing a generic balanced tree check is quite easy and elegant
  
you have to do two checks
  
1. depth of tree taking any path is the same
2. width of tree at any depth is the same
  
both these checks can be implemented without awareness of dht/afr/stripe so, build graph from existing volfile
  
prune out leaves based on the list of bricks to be removed normalize the graph (i.e, if a node has 0 subvolumes, take out that node - recursively upwards)
  
then check two constraints
  
1. graph is balanced
  
2. stripe degree has not decreased

this function will be so generic that tomorrow even if we re-architect volgen to cascade cluster xlators differently (says, stripe over afr over dht) even then it will work fine

3. if distributed degree is getting decreased, then unless it is a commit op, mark as decommissioned subvol
  
all these can be done very generically
Comment 2 Anand Avati 2011-10-28 09:42:11 UTC 
CHANGE: http://review.gluster.com/158 (with this patch, one can do all the below operations:) merged in master by Vijay Bellur (vijay)
Comment 3 Amar Tumballi 2011-10-28 09:46:22 UTC 
This feature is not going to be backported to release-3.2 version, and hence resolving this bug