Re: PATCH: track last known XLOG segment in control file - Mailing list pgsql-hackers

From Andres Freund
Subject Re: PATCH: track last known XLOG segment in control file
Date
Msg-id 20151212222023.GR14789@awork2.anarazel.de
Whole thread Raw
In response to PATCH: track last known XLOG segment in control file  (Tomas Vondra <tomas.vondra@2ndquadrant.com>)
Responses Re: PATCH: track last known XLOG segment in control file  (Tomas Vondra <tomas.vondra@2ndquadrant.com>)
List pgsql-hackers
Hi,

On 2015-12-12 22:14:13 +0100, Tomas Vondra wrote:
> this is the second improvement proposed in the thread [1] about ext4 data
> loss issue. It adds another field to control file, tracking the last known
> WAL segment. This does not eliminate the data loss, just the silent part of
> it when the last segment gets lost (due to forgetting the rename, deleting
> it by mistake or whatever). The patch makes sure the cluster refuses to
> start if that happens.

Uh, that's fairly expensive. In many cases it'll significantly increase
the number of fsyncs. I've a bit of a hard time believing this'll be
worthwhile. Additionally this doesn't seem to take WAL replay into
account?

Andres



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