On 14/03/18 11:47, Clay Gerrard wrote:

On Tue, Mar 13, 2018 at 3:05 PM, Mark Kirkwood <mark.kirkw...@catalyst.net.nz <mailto:mark.kirkw...@catalyst.net.nz>> wrote:

    To me this suggests that a certain minimum number of *hosts* per
    region is needed for a given EC policy to be durable in the advent
    of host outage (or destruction). Is this correct - or have a
    flubbed the calculations?

Looks correct to me.  Ideally you'd have more nodes per region than k+m; otherwise a reboot would mean WAN traffic - or if that's not possible - temporary unavailability.

Awesome thanks!

Doing a bit more playing about leads me to think that for a *single region* EC policy we can get a tighter lower bound on the number of hosts: I'm calculating it as (k+m)/m. So in the case I was playing with before (k=8, m=2), then I need 5 hosts in my region. While testing does seem to support this, does it sound reasonable?


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