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
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@xxxxxxxxxxx> To: gluster-users@xxxxxxxxxxxSent: Friday, March 31, 2017 3:34:35 AM Subject: Re: 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 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@xxxxxxxxx> To: "Terry McGuire" <tmcguire@xxxxxxxxxxx> Cc: gluster-users@xxxxxxxxxxx Sent: Thursday, March 30, 2017 11:57:27 AM Subject: Re: Node count constraints with EC?
> Le 29 mars 2017 à 20:29, Terry McGuire <tmcguire@xxxxxxxxxxx> 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.
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