Message-ID: <d56da8fc92109960f24fb805e17d1be5fe5d0adb.camel@cybertec.at>
Subject: Re: max_wal_size and wal_keep_size
From: Laurenz Albe <laurenz.albe@cybertec.at>
To: "James Pang (chaolpan)" <chaolpan@cisco.com>, Jeff Janes
	 <jeff.janes@gmail.com>
Cc: "pgsql-admin@lists.postgresql.org" <pgsql-admin@lists.postgresql.org>
Date: Tue, 30 Aug 2022 19:29:17 +0200
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On Tue, 2022-08-30 at 08:29 +0000, James Pang (chaolpan) wrote:
> We want keep more wal to give more room for data replication, in case of some delay ,
> and need old wal data. So wan to set wal_keep_size , and want to increase
> max_wal-size a lot to make max_wal_size > wal_keep_size (it may > 1TB).

The two parameters are independent:
- "max_wal_size" does *not* determine the maximum WAL size, but how much
  WAL can be produced before the next checkpoint is triggered.
- "wal_keep_size" determines how much old WAL is kept around.

Set "wal_keep_size" and leave "max_wal_size" unchanged.

Or even better, use a replication slot.

Yours,
Laurenz Albe
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