Re: Database size different on Primary and Standby?

2023年1月19日(木) 8:50 Erik Wienhold <ewie@ewie.name>:
>
> > On 19/01/2023 00:09 CET Hilbert, Karin <ioh1@psu.edu> wrote:
> >
> > I manage some PostgreSQL clusters on Linux. We have a Primary & two Standby
> > servers & for Production, there is also a DR server. We use repmgr for our HA
> > solution & the Standbys are cloned from the Primary using the repmgr standby
> > clone command.
> >
> > My manager asked for a report of all the user databases & their sizes for each
> > server in the cluster. I used the psql "\l+" command & then extracted the
> > database name & the size from the output. I expected the databases to be the
> > same size on the Standbys as on the Primary, but I found that some of the
> > databases were smaller on the Standby servers than on the Primary.
> >
> > For example, the output on the Primary for one of the user databases showed
> > as: 8997 kB, but on the Standbys, it was 8849 kB.
>
> The standbys could be missing some indexes because schema changes are not
> replicated and must be applied manually.

This is incorrect; with streaming replication all changes applied on the primary
are applied on the standby.

(...)
> Could also be different page sizes. But that's a compilation option. What does
> SHOW block_size say on those systems?

It is impossible to start a standby using binaries built with a
different block size to
the primary.

Regards

Ian Barwick