Let's assume that the new servers are Server C and Server D. In the above architecture diagram, we could notice that I have added 2 more servers to the existing replication cluster using streaming replication. To understand this better, see the following architecture diagram. For this reason, MigOps suggests you to add one or more new standby servers that can be used for the purpose of upgrade and enable the possibilities for faster rollback. While it is always recommended to perform a backup before performing any upgrade, it is equally important to have at least one stand-alone server that can be used for the purpose of a rollback. In this article, I have included 2 additional servers, because i want to make it more easier for rollback, without the need of risking the existing replication cluster. Choosing an Architecture that enables ROLLBACK capabilitiesĪs the hard links upgrade using pg_upgrade is an in-place upgrade, it is also important to enable the possibilities of rollback. A file or directory is nothing but a link to an inode. For this reason, this approach only works when the new target data directory is created on the same file system as the older one.Īn inode is a data structure contains the metadata about the disk block location. This way, there is no need of copying or moving data between the two data directories. However, these files and directories are pointed to the same inodes as the files and directories in the old directory. In this approach, pg_upgrade creates files and directories in the new data directory (used for latest or target PostgreSQL version) similar to the old data directory (Old or legacy PostgreSQL version). We have streaming replication setup between Primary and the Standby servers. Primary (Server A) to Standby (Server B). Let us consider a scenario where there exists a PostgreSQL replication cluster. PostgreSQL Setup considered in this article However, the approach for DBaaS will be covered in the subsequent articles. This approach does not work for DBaaS platforms like Amazon RDS or Azure database for PostgreSQL or Google Cloud SQL for PostgreSQL. Point to Note : This approach is only applicable if you are using PostgreSQL on dedicated or virtual servers like AWS EC2 or GCP Virtual machines or Azure Virtual machines.
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