I'm about to begin playing with incrementally updated backups for a warm standby scenario, but I need some help understanding this paragraph in postgres terms. From 23.4.5 in the 8.2.3 docs:
"If we take a backup of the standby server's files while it is following logs shipped from the primary, we will be able to reload that data and restart the standby's recovery process from the last restart point. We no longer need to keep WAL files from before the restart point. If we need to recover, it will be faster to recover from the incrementally updated backup than from the original base backup."
I'm specifically confused about the meaning of the following phrases:
"backup of the standby server's files" - Which files?
"reload that data" - What does this mean in postgres terms?
"last restart point" - What is this? Wouldn't it be able to restart from the last recovered file, which would presumably occur later than the last restart point?
Does this mean make a filesystem backup of the standby server's data directory while it's stopped, and then start it again with that data and the restricted set of WAL files needed to continue recovery? I'd like to see the language here converted to words that have more meaning in the context of postgres. I'd be happy to attempt a revision of this section once I'm able to complete an incrementally updated backup successfully.
Here's how I envision it playing out in practice:
1. stop standby postgres server
2. [optional] preserve data directory, remove unnecessary WAL files
3. restart standby server
Is that all there is to it?
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Thomas F. O'Connell
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