Date: Mon, 24 Apr 2017 21:17:43 -0700
From: Andres Freund <andres@anarazel.de>
To: pgsql-general@postgresql.org, pgsql-performance@postgresql.org
Subject: Questionaire: Common WAL write rates on busy servers.
Message-ID: <20170425041743.ddabv2mwevcmtx5a@alap3.anarazel.de>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
Precedence: bulk
Sender: pgsql-performance-owner@postgresql.org

Hi,

I've lately seen more and more installations where the generation of
write-ahead-log (WAL) is one of the primary bottlenecks.  I'm curious
whether that's primarily a "sampling error" of mine, or whether that's
indeed more common.

The primary reason I'm curious is that I'm pondering a few potential
optimizations, and would like to have some guidance which are more and
which are less important.

Questions (answer as many you can comfortably answer):
- How many MB/s, segments/s do you see on busier servers?
- What generates the bulk of WAL on your servers (9.5+ can use
  pg_xlogdump --stats to compute that)?
- Are you seeing WAL writes being a bottleneck?OA
- What kind of backup methods are you using and is the WAL volume a
  problem?
- What kind of replication are you using and is the WAL volume a
  problem?
- What are your settings for wal_compression, max_wal_size (9.5+) /
  checkpoint_segments (< 9.5), checkpoint_timeout and wal_buffers?
- Could you quickly describe your workload?

Feel free to add any information you think is pertinent ;)

Greetings,

Andres Freund


-- 
Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-performance