Re: Checksums and full_page_writes

On Fri, Dec 26, 2014 at 01:11:57PM +0300, Borodin Vladimir wrote:
> Hi all.
>
> I ve read thread [0], src/backend/storage/page/README and everything I found in
> the documentation about checksums [1, 2] but I haven t understood what is my
> risk if I enable checksums during initdb and turn off full_page_writes?
>
> Am I right that I can get torn pages on disk in that case but I will somehow
> know about it during checksum checking when this page will be read from disk to
> shared buffers? And is there any way to recover such torn page (from replica or

Yes.

> backup+archived logs, for example)?

There is no way to _fix_ the torn page, but you can ignore the error
with ignore_checksum_failure:

http://www.postgresql.org/docs/9.4/static/runtime-config-developer.html

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

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