From: Andres Freund <andres@anarazel.de>
To: pgsql-general@postgresql.org
To: pgsql-performance@postgresql.org
Subject: Questionaire: Common WAL write rates on busy servers.
Date: Mon, 24 Apr 2017 21:17:43 -0700
Message-ID: <20170425041743.ddabv2mwevcmtx5a@alap3.anarazel.de> (raw)
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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
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Cc: andres@anarazel.de, pgsql-general@postgresql.org
Subject: Re: Questionaire: Common WAL write rates on busy servers.
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