| From: | Dagfinn Ilmari Mannsåker <ilmari(at)ilmari(dot)org> |
|---|---|
| To: | Simon Riggs <simon(dot)riggs(at)enterprisedb(dot)com> |
| Cc: | Thomas Munro <thomas(dot)munro(at)gmail(dot)com>, Julien Rouhaud <rjuju123(at)gmail(dot)com>, Ashutosh Sharma <ashu(dot)coek88(at)gmail(dot)com>, Daniel Gustafsson <daniel(at)yesql(dot)se>, Stephen Frost <sfrost(at)snowman(dot)net>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Andres Freund <andres(at)anarazel(dot)de>, David Steele <david(at)pgmasters(dot)net>, Dmitry Dolgov <9erthalion6(at)gmail(dot)com>, Jakub Wartak <Jakub(dot)Wartak(at)tomtom(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: WIP: WAL prefetch (another approach) |
| Date: | 2022-04-12 15:57:41 |
| Message-ID: | 87tuaynvka.fsf@wibble.ilmari.org |
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| Lists: | pgsql-hackers |
Simon Riggs <simon(dot)riggs(at)enterprisedb(dot)com> writes:
> On Thu, 7 Apr 2022 at 08:46, Thomas Munro <thomas(dot)munro(at)gmail(dot)com> wrote:
>
>> With that... I've finally pushed the 0002 patch and will be watching
>> the build farm.
>
> This is a nice feature if it is safe to turn off full_page_writes.
>
> When is it safe to do that? On which platform?
>
> I am not aware of any released software that allows full_page_writes
> to be safely disabled. Perhaps something has been released recently
> that allows this? I think we have substantial documentation about
> safety of other settings, so we should carefully document things here
> also.
Our WAL reliability docs claim that ZFS is safe against torn pages:
https://www.postgresql.org/docs/current/wal-reliability.html:
If you have file-system software that prevents partial page writes
(e.g., ZFS), you can turn off this page imaging by turning off the
full_page_writes parameter.
- ilmari
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