| From: | Bruce Momjian <bruce(at)momjian(dot)us> |
|---|---|
| To: | Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com> |
| Cc: | Andres Freund <andres(at)anarazel(dot)de>, David Christensen <david(dot)christensen(at)crunchydata(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Stephen Frost <sfrost(at)snowman(dot)net> |
| Subject: | Re: Initdb-time block size specification |
| Date: | 2023-06-30 22:37:39 |
| Message-ID: | ZJ9ZMznPmBZItEot@momjian.us |
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| Lists: | pgsql-hackers |
On Sat, Jul 1, 2023 at 12:21:03AM +0200, Tomas Vondra wrote:
> On 6/30/23 23:53, Bruce Momjian wrote:
> > For a 4kB write, to say it is not partially written would be to require
> > the operating system to guarantee that the 4kB write is not split into
> > smaller writes which might each be atomic because smaller atomic writes
> > would not help us.
>
> Right, that's the dance we do to protect against torn pages. But Andres
> suggested that if you have modern storage and configure it correctly,
> writing with 4kB pages would be atomic. So we wouldn't need to do this
> FPI stuff, eliminating pretty significant source of write amplification.
I agree the hardware is atomic for 4k writes, but do we know the OS
always issues 4k writes?
--
Bruce Momjian <bruce(at)momjian(dot)us> https://momjian.us
EDB https://enterprisedb.com
Only you can decide what is important to you.
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