Date: Fri, 8 Nov 2019 15:50:25 +0100
From: Tomas Vondra <tomas.vondra@2ndquadrant.com>
To: Christoph Berg <myon@debian.org>,
	PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Subject: Re: Monitoring disk space from within the server
Message-ID: <20191108145025.d7pfcip6plufxiah@development>
References: <20191108132419.GG8017@msg.df7cb.de>
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On Fri, Nov 08, 2019 at 02:24:19PM +0100, Christoph Berg wrote:
>Monitoring the available disk space is the topmost thing on the
>priority for PostgreSQL operation, yet this metric is not available
>from the SQL level.
>

While I agree monitoring disk space is important, I think pretty much
every deployment already does that using some other monitoring tool
(which also monitors million other things).

Also, I wonder how universal / reliable this actually is, considering
the range of filesystems and related stuff (thin provisioning, quotas,
...) people use in production. I do recall a number of cases when "df"
was showing a plenty of free space, but one of the internal resources
for that particular filesystem was exhausted. I doubt it's desirable to
add all this knowledge into PostgreSQL.

It's not clear to me what issue this is actually meant to solve - it
provides data, which is nice, but it still needs to be fed to some
motinoring and alerting system. And every monitoring system has a good
plugin to collect this type of data, so why not to use that?

Surely, we can't rely on this for any internal logic - so why not to
provide this as an extension?


regards

-- 
Tomas Vondra                  http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services