Replication Modes Definitions?
I am currently examining different NoSQL and RDBMSes regarding their replication abilities in order to build distributed systems.
Reading through several papers and books, I get the feeling, that some vendors or authors use their own definitions regarding the terms
- Master-Master Replication (Replication between two servers)
- Master-Slave Replication (Replication between mutliple Servers in order to increase reading speed, writes are only able for the master server)
- Multi-Master Replication (= Peer-To-Peer?)
- Peer-To-Peer Replication (replication between n nodes, each can read/write)
- Merge Replication (?)
E.g: Some mix up the terms Master-Master and Peer-to-Peer as the same, while in Mysql docus for instance I found it is differentiated between Master-Master and Multi-Master (=Peer-to-peer???) Replication.
Where is the difference in Multi-Master and Peer-to-Peer replication? Is Multi-Master replication's use case more oriented towards Clustering while Peer-To-Peer targets distributed content to distributed applications?
I would like to sort things out and be sure that I have the right understanding in these terms, so maybe a discussion in here woul开发者_运维百科d help to merge some knowledge.
Regards, Chris
Edit: added merge replication to the list and some explanations as I understand them...
Regarding CouchDB, the story is simple. Here it is:
There is only one replication mode for CouchDB. The source copies all its data to the target, subject to an optional yes/no filter. I described CouchDB replication in another question. The key point is that "replication" is simply a DB client. It connects to both couches, reads from the source, and writes to the target.
Any other big-picture architecture (peer-to-peer, multi-master, master-slave) is just the implementation of the developers or the system administrators. For example, if GET
s are distributed to many couches, but POST
go to one central couch which replicates to the others, that is effectively master-slave. If you put a CouchDB in every major city for performance, and they replicate directly with each other, that is multi-master replication.
Within the CouchDB community, and especially from Chris Anderson's projects and presentations, "peer-to-peer" replication is a concept where CouchDB is everywhere: mobile phones, data centers, telephone poles. And replication happens directly between couches in a decentralized way, without a central authority or architecture, like the web itself.
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