Re: Unexplained disk usage in AWS Aurora Postgres

On Tue, Aug 4, 2020 at 4:39 AM Chris Borckholder <chris.borckholder@bitpanda.com> wrote:

Hi!

We are experiencing a strange situation with an AWS Aurora postgres instance.

The database steadily grows in size, which is expected and normal.

After enabling logical replication, the disk usage reported by AWS metrics increases much faster then the database size (as seen by \l+ in psql). The current state is that database size is ~290GB, while AWS reports >640GB disk usage.

We reached out to AWS support of course, which is ultimately responsible.

Unfortunately they were not able to diagnose this until now.

I checked with the queries from wiki https://wiki.postgresql.org/wiki/Disk_Usage , which essentially give the same result.

I tried to check on wal segment file size, but we have no permission to execute select pg_ls_waldir().

The replication slot is active and it also progresses (pg_replication_slots.confirmed_flush_lsn increases and is close to pg_current_wal_flush_lsn).

Can you imagine other things that I could check from within postgres with limited permissions to diagnose this?

Best Regards

Chris

If you do archive wal files, maybe the archive_command is failing?