Feedback-ID: i97614980:Fastmail
MIME-Version: 1.0
Date: Mon, 16 Feb 2026 12:06:56 +0100
From: "Pierre Barre" <pierre@barre.sh>
To: "Jeff Ross" <jross@openvistas.net>, pgsql-general@lists.postgresql.org
Message-Id: <dd5254f2-a308-4520-888e-e4f49a81a6ed@app.fastmail.com>
In-Reply-To: <60027457-1b85-4a69-a67e-ee87f7cabd61@openvistas.net>
References: <a9fe5ddb-9685-4139-bc1f-88161a7a4da3@app.fastmail.com>
 <CAG1bHGOzCNtDeW0W8gRO7mpW=t7BqWh-iz4kX5VRCPgt_6Tr6Q@mail.gmail.com>
 <8188513c-e089-4273-b2be-16dd0a5a0a80@app.fastmail.com>
 <aIKNLuEis1DQEOGv@ubby>
 <5c512367-0f67-4bcc-9897-1acf9c0f8bd3@app.fastmail.com>
 <60027457-1b85-4a69-a67e-ee87f7cabd61@openvistas.net>
Subject: Re: PostgreSQL on S3-backed Block Storage with Near-Local Performance
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: quoted-printable
Archived-At: <https://www.postgresql.org/message-id/dd5254f2-a308-4520-888e-e4f49a81a6ed%40app.fastmail.com>
Precedence: bulk

Hi all,

Circling back on this thread, ZeroFS now supports placing its WAL on loc=
al storage (or something like S3 Express One Zone). ZeroFS wal is sub-gi=
gabyte and just there to handle frequent syncs, it doesn't act as writeb=
ack caching.

Here are pgbench results with synchronous_commit =3D on, WAL on local NV=
Me, on a 6-core / 32GB RAM machine with a 4 Gb/s pipe:

$ pgbench -c 100 -T 100 --protocol=3Dprepared

transaction type: <builtin: TPC-B (sort of)>
scaling factor: 100
query mode: prepared
number of clients: 100
number of threads: 1
duration: 100 s
number of transactions actually processed: 1,578,675
number of failed transactions: 0 (0.000%)
latency average =3D 6.312 ms
tps =3D 15,843 (without initial connection time)

Best,
Pierre

On Fri, Jul 25, 2025, at 00:03, Jeff Ross wrote:
> On 7/24/25 13:50, Pierre Barre wrote:
>
>> It=E2=80=99s not =E2=80=9Csafe=E2=80=9D or =E2=80=9Cunsafe=E2=80=9D, =
there=E2=80=99s mountains of valid workloads which don=E2=80=99t require=
 synchronous_commit. Synchronous_commit don=E2=80=99t make your system a=
utomatically safe either, and if that=E2=80=99s a requirement, there=E2=80=
=99s many workarounds, as you suggested, it certainly doesn=E2=80=99t ma=
ke the setup useless.
>>
>> Best,
>> Pierre
>>
>> On Thu, Jul 24, 2025, at 21:44, Nico Williams wrote:
>>> On Fri, Jul 18, 2025 at 12:57:39PM +0200, Pierre Barre wrote:
>>>> - Postgres configured accordingly memory-wise as well as with
>>>>    synchronous_commit =3D off, wal_init_zero =3D off and wal_recycl=
e =3D off.
>>> Bingo.  That's why it's fast (synchronous_commit =3D off).  It's als=
o why
>>> it's not safe _unless_ you have a local, fast, persistent ZIL device
>>> (which I assume you don't).
>>>
>>> Nico
>>> --
> This then begs the obvious question of how fast is this with=20
> synchronous_commit =3D on?