Re: Restoration process generates 1.2 TB of WAL files.

On Wed, Jan 28, 2026 at 2:16 PM Wasim Devale <wasimd60(at)gmail(dot)com> wrote:

> Hi All
>
> I am taking directory dump from postgresql 12 and restoring it on
> postgresql 17 this process create 1.2TB of wals files in pg_wal directory.
> Can we reduce this WAL files generation via any configuration changes?
>

Sure. This is what I used when restoring some 3+ TB databases. (Your
values for $SharedBuffs and $MaintMem will vary based on how much RAM
you have and how many threads you use in pg_restore.)

Setting $SharedBuffs and (especially) $MaintMem too high will cause the
Linux oom-killer to kill one or more of the CREATE INDEX or ADD PRIMARY KEY
statements, and you'll scratch your head looking at the pg_restore log file
wondering what happened.

I based it on:
https://www.databasesoup.com/2014/09/settings-for-fast-pgrestore.html

pg_ctl restart -wt$TimeOut -mfast \
-o "-c hba_file=$PGDATA/pg_hba_maintmode.conf" \
-o "-c fsync=off" \
-o "-c log_statement=none" \
-o "-c log_temp_files=100kB" \
-o "-c log_checkpoints=on" \
-o "-c log_min_duration_statement=120000" \
-o "-c shared_buffers=${SharedBuffs}GB" \
-o "-c maintenance_work_mem=${MaintMem}GB" \
-o "-c synchronous_commit=off" \
-o "-c archive_mode=off" \
-o "-c full_page_writes=off" \
-o "-c checkpoint_timeout=30min" \
-o "-c max_wal_size=36GB" \
-o "-c wal_level=minimal" \
-o "-c max_wal_senders=0" \
-o "-c wal_buffers=64MB" \
-o "-c autovacuum=off" || exit $?
pg_restore --verbose --jobs=X ... &> pg_restore.log || exit $?
pg_ctl stop -wt9999 && pg_ctl start -wt9999

These are "bad" settings if you have other databases in your instance and
they need to keep running while you restore your DB. *I don't have that *
*problem*, so think it's great.

--
Death to <Redacted>, and butter sauce.
Don't boil me, I'm still alive.
<Redacted> lobster!