Re: journaled FS and and WAL - Mailing list pgsql-general

From Michael Paquier
Subject Re: journaled FS and and WAL
Date
Msg-id CAB7nPqSk3q0vjK=X3wK=Fw05WFOcJByXMtiOvBPXA84HvPi-Aw@mail.gmail.com
Whole thread Raw
In response to Re: journaled FS and and WAL  (Albe Laurenz <laurenz.albe@wien.gv.at>)
Responses Re: journaled FS and and WAL  ("t.dalpozzo@gmail.com" <t.dalpozzo@gmail.com>)
List pgsql-general
On Fri, Oct 14, 2016 at 11:27 PM, Albe Laurenz <laurenz.albe@wien.gv.at> wrote:
> After a successful commit, the WAL file and its metadata are on disk.
> Moreover, the file metadata won't change (except for the write and access
> timestamps) because WAL files are created with their full size and never
> extended, so no WAL file should ever get "lost" because of partial metadata
> writes.

This behavior depends as well on the value of wal_sync_method. For
example with fdatasync the metadata is not flushed. It does not matter
any for for WAL segments as Albe has already mentioned, but the choice
here impacts performance.
--
Michael


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