On Mon, Jan 27, 2014 at 12:35 PM, Sameer Kumar <sameer.ku...@ashnik.com>wrote:
> > On Mon, Jan 27, 2014 at 11:24 AM, Michael Paquier < > michael.paqu...@gmail.com> wrote: > >> PostgreSQL supports synchronous multi-master, MongoDB supports write >>>> concern, but this causes a performance penalty). >>> >>> Anyways I doubt that "PostgreSQL supports synchronous multi-master" >>> >> Postgres core taken as such does not support multi-master. The fork of >> PostgreSQL called Postgres-XC somewhat does, for OLTP applications. >> > > I know about PostgresXC, but I thought it is distributed database (similar > to shards of mongoDB). [Though if I am correct there could be tables which > are shared across different nodes, but that is not the best way of > utilizing features of PostgresXC] I think it is not apt to call it > "synchronous" (since there is no replication happening). > XC supports table sharding with distribution of data using a column key, or even data replication. Table definitions and schemas are the same across all the nodes, it is just that the data is present in a portion of the nodes (Datanodes more precisely) of the cluster. Operations are done *synchronously* through the cluster using what is called a GTM (global transaction manager) that is unique and feeds all the other nodes with globally-consistent transaction IDs and snapshots. GTM SPOF is solved with the presence of a Standby. -- Michael
