Re: PG12: Any drawback of increasing wal_keep_segments

Greetings,

On Thu, Mar 31, 2022 at 12:58 Marc <postgres(at)arcict(dot)com> wrote:

> On 29 Mar 2022, at 17:17, Stephen Frost wrote:
>
> Greetings,
>
> - Alvaro Herrera (alvherre(at)alvh(dot)no-ip(dot)org) wrote:
>
> On 2022-Mar-22, Shukla, Pranjal wrote:
>
> Are there any disadvantages of increasing the “wal_keep_segments” to a
> higher number say, 500? Will it have any impact on performance of
> streaming replication, on primary or secondary servers?
>
> No. It just means WAL will occupy more disk space. I've seen people go
> even as high as 5000 with no issues.
>
> Yeah, though it makes the primary into essentially a WAL repository and,
> really, you'd be better off having a dedicated repo that replicas can
> pull from instead. Consider that a replica might fall way behind and
> then demand the primary send 5000 WAL segments to it. The primary then
> has to go pull that 80GB of data from disk and send it across the
> network. As to if that's an issue or not depends on the IOPS and
> bandwidth available, of course, but it's not free.
>
> Thanks,
>
> Stephen
>
> Hello Stephen,
>
> How do you see a setup with a ‘a dedicated repo that replicas can pull
> from’ ?
>
> Thanks in advance for the clarification.
>
I’d suggest checking out pgbackrest. There are other options out there but
that’s my favorite (probably because I also am one of the folks involved in
its development, full disclosure).

Thanks,

Stephen

>