On Thu, Mar 31, 2016 at 11:26 AM, Marcelo E. Magallon < marcelo.magal...@hpe.com> wrote:
> Hi Ben, > > On 03/30/2016 06:13 PM, Ben Pfaff wrote: > > I understand the technical differences between the approaches. My question >> is whether high availability is your actual goal. If it is, then it >> probably does not make sense to have multiple implementations. If you are >> trying to accomplish something else, then it could be that there is >> something complementary about the two implementations. >> > > I believe the two approaches are complementary. > > Like I said, the proposed patch aims at having a stand by database > available, but since there's no proxy or anything like that, if the active > database goes down, clients would have to reconnect. Ideally, after > failover, the stand-by database becomes the active and clients can reuse > the same connection parameters, but a reconnection must happen. If someone > is interested in filling that gap, haproxy is an option, but I have not yet > tested it. Same thing applies to a Raft-based solution. > > What you are doing with Raft is complementary in the sense that you can > have six database servers, expose three of them to the clients and the > other three become stand-bys for the three active ones. If any of the three > actives go down, the corresponding stand-by steps up. With Raft, with 6 > active databases, you can loose 2 (4 are needed for consensus). With this > approach you only have 3 databases in service, but you can loose all three. > Obviously you can come up with other topologies like 3+1, or 5+1, etc. The > proposed patch is the "+" part in that design. I don't understand the value of combining the two in the same installation. This all just sounds like an active-passive versus active-active HA solution. Active-passive seems a bit easier to implement, but I would always prefer the active-active solution if it's available. The one thing this approach would provide is an HA solution for 2 nodes instead of at least 3. We're already using at least 3 nodes for HA reasons in all of the environments that I care about for my use cases since we need 3 for other active-active solutions. Do you have a requirement for a 2-node solution? Could you expand on your use case? -- Russell Bryant _______________________________________________ dev mailing list dev@openvswitch.org http://openvswitch.org/mailman/listinfo/dev
