From: Tom Lane <tgl@sss.pgh.pa.us>
To: Don Seiler <don@seiler.us>
Cc: Postgres General <pgsql-general@postgresql.org>
Subject: Re: Use of max_slot_wal_keep_size parameter
Date: Tue, 26 Mar 2024 10:29:21 -0400
Message-ID: <2821429.1711463361@sss.pgh.pa.us> (raw)
In-Reply-To: <CAHJZqBB5E4gF18PSOqHph+uXQ+HP5uRqf1S1MYekbSspO_VRbw@mail.gmail.com>
References: <CAHJZqBArXQ0245uvwdBa+ax520BjgRNEuTdFXbnuDwyaJbxUAg@mail.gmail.com>
<2818930.1711462144@sss.pgh.pa.us>
<CAHJZqBB5E4gF18PSOqHph+uXQ+HP5uRqf1S1MYekbSspO_VRbw@mail.gmail.com>
Don Seiler <don@seiler.us> writes:
> On Tue, Mar 26, 2024 at 9:09 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> ... So you could overshoot the specified target by
>> more or less the amount of WAL that could be emitted between two
>> checkpoints. Perhaps it's tighter nowadays, but I really doubt that
>> it's exact-to-the-kilobyte-at-all-times.
> In this case, the total volume size was 60GB and we had the parameter set
> to 58GB but I imagine that can still be overwhelmed quickly. Maybe we
> should target a 20% buffer zone? We have wal_keep_size defaulted at 0.
Can you measure your WAL emission rate? What you want I think is some
small multiple of the max amount of WAL emitted between checkpoints.
regards, tom lane
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To: pgsql-general@postgresql.org
Cc: tgl@sss.pgh.pa.us, don@seiler.us
Subject: Re: Use of max_slot_wal_keep_size parameter
In-Reply-To: <2821429.1711463361@sss.pgh.pa.us>
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