PostgreSQL — кластеры


Postgres-XC is an open source project to provide write-scalable, synchronous symmetric, transparent PostgreSQL cluster solution. It is a collection if tightly coupled database components which can be installed in more than one hardware or virtual machines.

Write-scalable means Postgres-XC can be configured with as many database servers as you want and handle much more writes (updating SQL statements) which single database server cannot do. Symmetric means you can have more than one data base servers which provide single database view. Synchronous means any database update from any database server is immediately visible to any other transactions running in different masters. Transparent means you don’t have to worry about how your data is stored in more than one database servers internally. [1]

You can configure Postgres-XC to run on more than one machines. They store your data in a distributed way, that is, partitioned or replicated way at your choice for each table. [2] When you issue queries, Postgres-XC determines where the target data is stored and issue corresponding queries to servers with the target data.

In typical web systems, you can have as many web servers or application servers to handle your transactions. However, you cannot do this for a database server in general because all the changing data have to be visible to all the transactions. Unlike other database cluster solution, Postgres-XC provides this capability. You can install as many database servers as you like. Each database server provides uniform data view to your applications. Any database update from any server is immediately visible to applications connecting the database from other servers. This feature is called «synchronous multi master» capability and this is the most significant feature of Postgres-XC.

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