Re: does postgresql backup require additional space on disk

On Mon, May 13, 2019 at 07:33:58PM +0000, Julie Nishimura wrote:

> We have added new disk volume and about to introduce new
> tablespace using this additional disk space. After that, I am
> going to alter all user dbs (and template db as well) by
> runnig the following command:
>
> CREATE TABLESPACE vol4
> OWNER postgres
> LOCATION '/data/vol4';
>
> ALTER DATABASE user_db_1
> SET default_tablespace = 'vol4';
>
> ...for all dbs..
>
> We have more than 70 different databases (the entire server
> is about 20 tb). However, for the largest dbs (16tb, 4 tb,
> and 3 tb), we do not have valid backups, unfortunately. So,
> we were debating if we need to run backups first before
> introducing all these changes. But we have only 1% left
> (about 200 gb).

You could move those databases first for which you do have
backups which should free up space in the old tablespace.
Then take backups of and move the remaining databases,
perhaps one by one.

Karsten
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