From: | Erik Wienhold <ewie(at)ewie(dot)name> |
---|---|
To: | Ian Lawrence Barwick <barwick(at)gmail(dot)com> |
Cc: | "Hilbert, Karin" <ioh1(at)psu(dot)edu>, "pgsql-general(at)lists(dot)postgresql(dot)org" <pgsql-general(at)lists(dot)postgresql(dot)org> |
Subject: | Re: Database size different on Primary and Standby? |
Date: | 2023-01-19 00:47:07 |
Message-ID: | 1018934732.57323.1674089227907@office.mailbox.org |
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Lists: | pgsql-general |
> On 19/01/2023 01:23 CET Ian Lawrence Barwick <barwick(at)gmail(dot)com> wrote:
>
> 2023年1月19日(木) 8:50 Erik Wienhold <ewie(at)ewie(dot)name>:
> >
> > > On 19/01/2023 00:09 CET Hilbert, Karin <ioh1(at)psu(dot)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.
Thanks. I was thinking about logical replication.
> (...)
> > 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.
Makes sense for streaming replication.
--
Erik
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