Physics of high temperatures
All probably already noticed that in PostgreSQL 8.4 appeared the new mode database: Warm standby. When it during operation of the database Write-Ahead logs (WAL) are broadcast into the subject database where real-time apply, as if it had occurred on the primary system. Therefore, if the main database for some reason (lightning/tornado/third world war/other disaster) fails, it will be possible to instantly switch to a subordinate database (which will be quite relevant compared to the main base) and use it in the future.
But, unfortunately, "warm stendbay" implies that the sub-system continuously occurs, the database recovery process; it follows that while the main base is alive, sub-base can not be used.
If you read at least blog depesz (not to mention the commit logs), then you already know what I'm getting at; if not, then... the 19th of December last year in a development version of PostgreSQL 8.5 has been added Hot standby. Now, when setting up WAL replication, the slave database can be used to SELECT queries (only SELECT, for obvious reasons). If before the second server to the second database idled in anticipation of force majeure, and admin had to blush in front of managers when questions about the effectiveness of the equipment — now this server is in the proper construction logic applications will help to unload the main database.
Details about the operation of the Hot standby can be read in corresponding article from the documentation for the development version of PostgreSQL.
Article based on information from habrahabr.ru
But, unfortunately, "warm stendbay" implies that the sub-system continuously occurs, the database recovery process; it follows that while the main base is alive, sub-base can not be used.
If you read at least blog depesz (not to mention the commit logs), then you already know what I'm getting at; if not, then... the 19th of December last year in a development version of PostgreSQL 8.5 has been added Hot standby. Now, when setting up WAL replication, the slave database can be used to SELECT queries (only SELECT, for obvious reasons). If before the second server to the second database idled in anticipation of force majeure, and admin had to blush in front of managers when questions about the effectiveness of the equipment — now this server is in the proper construction logic applications will help to unload the main database.
Details about the operation of the Hot standby can be read in corresponding article from the documentation for the development version of PostgreSQL.
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