Re: PostgreSQL Read IOPS limit per connection

 

Performance issue:

I’m trying to figure out if PostgreSQL (PG) has some inherent limit on IOPS per connection.

Running pgbench with multiple clients (-c 30) we are able to see 20K+ IOPS , which is what we expect. But, if we use just one client, we get 1200 IOPS, avg disk queue size around 1:

One of the issues I’m trying to solve is related to extracting data from a large table, which users a full table scan. We see the same 1200 IOPS limit of pgbench when we SELECT on this table using just one connection. If there is a limitation per connection, I might set up the application to have several connections, and then issue SELECTs for different sections of the table, and later join the data, but it looks cumbersome, especially if the DB can do extract data using more IOPS.