[Bugs] [Bug 1517260] Volume wrong size

[bugzilla at redhat.com]

https://bugzilla.redhat.com/show_bug.cgi?id=1517260



--- Comment #7 from Nithya Balachandran <nbalacha at redhat.com> ---
(In reply to david from comment #6)
> (In reply to Nithya Balachandran from comment #4)
> > (In reply to david from comment #0)
> > > Hi,
> > > I have a volume replica 3 distributed in 3 servers, the 3 severs have the
> > > same version (3.12.3) and the same SO (Ubuntu 16.04.1), each server has
> > > three bricks and I used this command to create the volume:
> > > 
> > > gluster volume create volume1 replica 3 transport tcp
> > > ubuntu1:/work/work1/test-storage1 ubuntu1:/work/work2/test-storage2
> > > ubuntu1:/work/work3/test-storage3 ubuntu2:/work/work1/test-storage1
> > > ubuntu2:/work/work2/test-storage2 ubuntu2:/work/work3/test-storage3
> > > ubuntu3:/work/work1/test-storage1 ubuntu3:/work/work2/test-storage2
> > > ubuntu3:/work/work3/test-storage3
> > > 
> > > Each brick has a size of 22TB,so I understand that if I mount the volume I
> > > should have a partition of 66TB. The problem is once the partition is
> > > mounted, if I check the size, appears that it has only 22TB..
> > > 
> > > I don't know what it's wrong, can anyone help me?
> > > 
> > > Thanks!!
> > 
> > On a different note - this is not the best way to create a replica 3 volume.
> > All you replicas are on the same host so if any one host goes down you lose
> > access to all the data on that replica set.
> > 
> > A better way is:
> > 
> > gluster volume create volume1 replica 3 transport tcp
> > ubuntu1:/work/work1/test-storage1 ubuntu2:/work/work1/test-storage1 
> > ubuntu3:/work/work1/test-storage1 ubuntu1:/work/work2/test-storage2
> > ubuntu2:/work/work2/test-storage2 ubuntu3:/work/work2/test-storage2
> > ubuntu1:/work/work3/test-storage3 ubuntu2:/work/work3/test-storage3 
> > ubuntu3:/work/work3/test-storage3
> 
> Hi @Nithya!
> 
> This is the same configuration that i have, isn't it? but in other order..
> 

Yes, but the ordering is what determines which bricks form a replica set
(contain copies of the same file). Ideally, you want to create your volume so
that you have each brick of a replica set on a different node so if one node
goes down the other 2 bricks on the other 2 nodes can still serve the data.


In the volume create command, with a replica value of 'n', each group of n
bricks forms a replica set. The first set of n bricks forms one set, then the
next n and so on. So in your case, the first 3 bricks passed to the create
command form a replica set, then the next 3 and so on. As the first 3 bricks
are all on the same node, if ubuntu1 goes down, all the files on that set will
be inaccessible. You can confirm this by checking the bricks on ubuntu1 - you
should see the same files on all 3 bricks.


> Thanks!

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