Hello!
I've some questions around Backup & Restore.
1: Is it necessary to perform a VACUUM and REINDEXING operation after restoring the dump from Postgres 9.6 to Postgres 13? The dump size could be 1/2 TB to 1 TB.
Perform VACUUM after there have been many updates and deletes. There have been zero updates and deleted after pg_restore; therefore, no need to vacuum.
pg_restore loads all tables and then builds all indices. Thus, no need to reindex.
2: Also, are there any other operations that are recommended to perform after pg_restore?
ANALYZE all tables.
https://www.postgresql.org/docs/13/app-vacuumdb.html
vacuumdb --dbname=whatever --jobs=`nproc` --analyze-only
3: What is the minimum required disk space if taking a dump on the same machine where the source database exists? Is it the "size of the current data folder x 2"?
Probably much less, but maybe (if, for example, you store lots of images (JPEG, TIFF, PDF, etc) in bytea columns.
Whatever you do, make sure to run pg_dump with these options: --format=directory --jobs=`nproc`
https://www.postgresql.org/docs/13/app-pgdump.html
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