We have a Postgres 13 database that has been slowly but steadily increasing its disk usage on Amazon RDS. Right before a VACUUM(FULL, ANALYZE, VERBOSE) command it was ~300 GB, but afterwards it jumped ~50% up to ~450GB.

We would like to reclaim that disk usage, since it's hard to imagine for me how Postgres is actually requiring that extra amount after a vacuum full.

How to analyse the root cause of the increase of disk usage following a vacuum full on the RDS Postgres? And how to reduce it again?

If you need key pieces of information to help answer the question, let me know in the comments below.

  • How are you measuring it? Maybe it is transient space, like WAL files waiting to be archived or streamed.
    – jjanes
    Commented May 25, 2022 at 12:46
  • Purely by what the RDS Management Console is reporting about the DB instance. It says Storage=451 GiB. Can I investigate if such processes are waiting and how to expedite their completion? Commented May 25, 2022 at 13:19
  • If connected by psql, you can use \l+ to see how big each database is. If that total is much less than 450GB, then the rest must be WAL or human-readable log files or something global like that. There may also be RDS-specific ways to check, but I wouldn't know what those are.
    – jjanes
    Commented May 25, 2022 at 18:51


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