"Hot standby"?

From: Peter Eisentraut <peter_e(at)gmx(dot)net>
To: pgsql-hackers(at)postgresql(dot)org
Subject: "Hot standby"?
Date: 2009-08-11 09:30:58
Message-ID: 200908111230.58135.peter_e@gmx.net
Views: Raw Message | Whole Thread | Download mbox | Resend email
Thread:
Lists: pgsql-hackers

What is "hot" and "standby" about the proposed "hot standby" feature?

The way I understand these terms in a replication/cluster scenario are:

cold - If the first node dies, you need to start the replacement node from a
standing start.

warm - If the first node dies, the replacement node needs to do some work to
get ready, but it's a lot quicker than "cold".

hot - If the first node dies, the replacement node can take over immediately.

standby - While the master node is running, the standby node instance cannot
be used for anything (useful).

slave - While the master node is running, the slave node can be used in
limited capacity (typically read-only).

master - Both/all nodes have equivalent capabilities all the time while the
cluster is up.

For example, I'd say that a DRBD-based solution would be a cold standby.
Among WAL-based solutions, what we have now with pg_standby (nomen est omen),
is a warmish standby. From what I understand, Simon's patch set does not
change the "warm" property of this arrangement at all. It only changes the
"standby" to a "slave".

Am I off? What other definition of terms justifies the description of "hot
standby"?

Responses

Browse pgsql-hackers by date

  From Date Subject
Next Message Brendan Jurd 2009-08-11 09:40:41 Re: WIP: to_char, support for EEEE format
Previous Message Peter Eisentraut 2009-08-11 08:31:30 Re: Filtering dictionaries support and unaccent dictionary