On 5/13/19 12:33 PM, 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:
Not sure why you need to move the template db's they
sure not take much
space?
More comments below.
>
> 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).
I have no experience with a setup of this size, someone
else will have
to provide real world advice. I would say taking a
backup before
preceding is a good idea. Pretty sure time is going to
be as much an
issue as space. This would apply to below also. The
question is what
options you have to bring cluster or databases down? In
particular for
below as:
https://www.postgresql.org/docs/11/sql-alterdatabase.html
"The fourth form changes the default tablespace of the
database. Only
the database owner or a superuser can do this; you must
also have create
privilege for the new tablespace. This command
physically moves any
tables or indexes in the database's old default
tablespace to the new
tablespace. The new default tablespace must be empty for
this database,
and no one can be connected to the database. Tables and
indexes in
non-default tablespaces are unaffected."
>
> What would you suggest? How would you classify the
risk of this
> operation (creating new tablespace and altering dbs
to use it)?
>
> Thanks,
> Julie
>
>
------------------------------------------------------------------------
> *From:* Adrian Klaver
<adrian.klaver@xxxxxxxxxxx>
> *Sent:* Monday, May 13, 2019 11:19 AM
> *To:* Julie Nishimura;
pgsql-general@xxxxxxxxxxxxxxxxxxxx; pgsql-general
> *Subject:* Re: does postgresql backup require
additional space on disk
> On 5/13/19 10:59 AM, Julie Nishimura wrote:
>> Hello,
>> we are almost out of disk space on one of our
servers (99% full). If we
>> run pg_dump to a diff location, does it require
any additional disk
>> space on our current server? I am asking,
because on some other
>> software, a backup might open transaction which
keeps growing and
>> eventually consume all space, keeping tran open
for the backup duration.
>> Please clarify? Thanks
>
> A pg_dump is a point in time snapshot of the
database, so if the cluster
> is running then it will advance past the dump
snapshot. If the cluster
> is not active(close off connections to all but
pg_dump) then pg_dump
> will be the only transaction.
>
> I think the first thing to ask is what you are
trying to achieve?
>
> --
> Adrian Klaver
>
adrian.klaver@xxxxxxxxxxx
--
Adrian Klaver
adrian.klaver@xxxxxxxxxxx
