On Wed, Mar 30, 2016 at 06:03:27PM -0600, Marcelo E. Magallon wrote: > On 03/30/2016 05:27 PM, Ben Pfaff wrote: > >I'm in the midst of implementing high availability for OVSDB, based on > >the Raft algorithm. When I'm done, it should be possible to set up > >OVSDB clusters with automatic failover. Is this the same use case as > >your code? > > No, in this case the replication works by way of making the second server an > OVSDB client, so it gets notified about all the changes in the remote > server.
Yes, I understand that the technical effect is not the same. Replication is much simpler and does not have the same characteristics. > In your case, how many OVSDB servers are required for replication to work? > Raft has a quorum requirement of (N/2)+1 servers to be available in order > for consensus to be reached. That makes the minimum number of servers 3, if > you want to allow one to become unavailable. If you have 2 servers and one > goes down, there's no quorum. Yes, this is correct, of course. > The patch Mario is proposing has failover characteristics, not > load-distribution characteristics: if one of the servers goes down, the > other one can take over because it has a copy of the data up to the last > notification the server was able to sent. Also, in the proposed patch > transactions are not delayed until consensus is reached, but instead clients > are talking only to the active server, which is applying transactions > immediately. The active server is notifying the standby about the new data > just like it's doing with any other client. 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. _______________________________________________ dev mailing list dev@openvswitch.org http://openvswitch.org/mailman/listinfo/dev
