Re: Setting up streaming replication on large database (20+ TB) for the first time

pg_backrest will certainly backup your data faster. It might be able to be
used as a seed instead of pg_basebackup.

On 8/17/22 15:06, Ivan N. Ivanov wrote:
> I have a large database (~25 TB) and I want to set up streaming
> replication for the first time.
>
> My problem is that after completion of the pg_basebackup (which completed
> for 2 days with --wal-method=none) now PG is replaying the WAL files from
> the WAL archive directory but it can not keep up. The replaying of WAL
> files is the same as the physical time, for example:
>
> 2022-08-17 22:42:57 EEST [13507-6] [] DETAIL:  Last completed transaction
> was at log time 2022-08-15 18:24:02.155289+03.
> 2022-08-17 22:48:35 EEST [13507-12] [] DETAIL:  Last completed transaction
> was at log time 2022-08-15 18:29:54.962822+03.
> 2022-08-17 22:54:35 EEST [13507-16] [] DETAIL:  Last completed transaction
> was at log time 2022-08-15 18:34:20.099468+03.
>
> From ~22:43 to ~22:48 there are 5 minutes. And completed transactions are
> at ~18:24 and ~18:29 (5 minutes).
>
> I have even put all WAL files from the archive directly in the pg_wal
> directory of the replica and now PostgreSQL skips the cp command from
> restore_command, i.e. I have removed the restore_command and now the WAL
> files are only recovering, this is the only operation, but it is slow:
>
> postgres: startup   recovering 000000010003FC7900000013
> postgres: startup   recovering 000000010003FC7900000014
> postgres: startup   recovering 000000010003FC7900000015
> ...
>
> And it cannot keep up and my replication cannot start since it is 2 days
> behind the master... The replica has the same SSD disks as the master.
>
> Is there a better way to do this? How to speed up recovering of WAL files?
> I have increased shared_buffers as much as I can... Is there something
> that I miss from the recovery process?
>
> I do not have problems setting up replications for the first time for
> small database (10 GB - 100 GB), but for 25 TB I can not set the
> replication, because of this lag.
>

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