Message-ID: <f08b1edf09b40062d355225fe1502ecf04571075.camel@cybertec.at>
Subject: Re: filesystem full during vacuum - space recovery issues
From: Laurenz Albe <laurenz.albe@cybertec.at>
To: Thomas Simpson <ts@talentstack.to>, pgsql-admin@lists.postgresql.org
Date: Tue, 16 Jul 2024 02:58:43 +0200
In-Reply-To: <d141b2e2-797c-487a-b492-e4fbeeafad3e@talentstack.to>
References: <d141b2e2-797c-487a-b492-e4fbeeafad3e@talentstack.to>
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On Mon, 2024-07-15 at 14:47 -0400, Thomas Simpson wrote:
> I have a large database (multi TB) which had a vacuum full running but th=
e database
> ran out of space during the rebuild of one of the large data tables.
>=20
> Cleaning down the WAL files got the database restarted (an archiving prob=
lem led to
> the initial disk full).
>=20
> However, the disk space is still at 99% as it appears the large table reb=
uild files
> are still hanging around using space and have not been deleted.
>=20
> My problem now is how do I get this space back to return my free space ba=
ck to where
> it should be?
>=20
> I tried some scripts to map the data files to relations but this didn't w=
ork as
> removing some files led to startup failure despite them appearing to be u=
nrelated
> to anything in the database - I had to put them back and then startup wor=
ked.
>=20
> Any suggestions here?

That reads like the sad old story: "cleaning down" WAL files - you mean del=
eting the
very=C2=A0files that would have enabled PostgreSQL to recover from the cras=
h that was
caused by the full file system.

Did you run "pg_resetwal"?  If yes, that probably led to data corruption.

The above are just guesses.  Anyway, there is no good way to get rid of the=
 files
that were left behind after the crash.  The reliable way of doing so is als=
o the way
to get rid of potential data corruption caused by "cleaning down" the datab=
ase:
pg_dump the whole thing and restore the dump to a new, clean cluster.

Yes, that will be a painfully long down time.  An alternative is to restore=
 a backup
taken before the crash.

Yours,
Laurenz Albe