[Gluster-users] Node count constraints with EC?

[Terry McGuire]

Ok, I think I see my error.  The rule, near as I can tell, is actually total/parity>2.  So, 4+2 gives 6/2=3, and therefore is ok.  Eventually I’ll get all this straight!

Terry


> On Mar 30, 2017, at 23:13, Ashish Pandey <aspandey at redhat.com> wrote:
> 
> Terry,
> 
> It is  (data/parity)>=2. You can very well create 4+2 or 8+4 volume.
> Are you seeing any error message that you can not create 4+2 config? (4 = data brick and 2 = redundancy brick count)
> 
> Ashish
> 
> From: "Terry McGuire" <tmcguire at ualberta.ca>
> To: gluster-users at gluster.org
> Sent: Friday, March 31, 2017 3:34:35 AM
> Subject: Re: [Gluster-users] Node count constraints with EC?
> 
> Thanks Ashish, Cedric, for your comments.
> 
> I’m no longer concerned about my choice of 4 nodes to start, but, I realize that there’s an issue with my subvolume config options.  Turns out only my 8+3 choice is permitted, as the 4+2 and 8+4 options violate the data/parity>2 rule.  So, 8+3 it is, as 8+2 isn’t quite enough redundancy for me.
> 
> Regards,
> Terry
> 
> 
> On Mar 30, 2017, at 02:14, yipikai7 at gmail.com <mailto:yipikai7 at gmail.com> wrote:
> 
> On 30/03/2017 08:35, Ashish Pandey wrote:
> Good point Cedric!!
> The only thing is that, I would prefer to say "bricks" instead of "nodes" in your statement.
> 
> "starting with 4 bricks (3+1) can only evolve by adding 4 bricks (3+1)" 
> Oh right, thanks for correcting me !
> 
> Cheers
> 
> 
> From: "Cedric Lemarchand" <yipikai7 at gmail.com> <mailto:yipikai7 at gmail.com>
> To: "Terry McGuire" <tmcguire at ualberta.ca> <mailto:tmcguire at ualberta.ca>
> Cc: gluster-users at gluster.org <mailto:gluster-users at gluster.org>
> Sent: Thursday, March 30, 2017 11:57:27 AM
> Subject: Re: [Gluster-users] Node count constraints with EC?
> 
> 
> > Le 29 mars 2017 à 20:29, Terry McGuire <tmcguire at ualberta.ca> <mailto:tmcguire at ualberta.ca> a écrit :
> > 
> > I was thinking I’d spread these over 4 nodes, and add single nodes over time, with subvolumes rearranged over new nodes to maintain protection from whole node failures.
> 
> Also keep in mind that dispersed cluster can only be expanded by the number of initial nodes, eg starting with 4 nodes 3+1 can only evolve by adding 4 nodes 3+1, you cannot change the default policy 3+1 to 4+1. So the granularity of the evolution of the cluster is fixed at the beginning. 
> 
> Cheers
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