| From: | Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com> |
|---|---|
| To: | Andres Freund <andres(at)2ndquadrant(dot)com> |
| Cc: | Ants Aasma <ants(at)cybertec(dot)at>, Hannu Krosing <hannu(at)2ndquadrant(dot)com>, Sameer Thakur <samthakur74(at)gmail(dot)com>, Amit Kapila <amit(dot)kapila(at)huawei(dot)com>, Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, sthomas(at)optionshouse(dot)com, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Samrat Revagade <revagade(dot)samrat(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Inconsistent DB data in Streaming Replication |
| Date: | 2013-04-12 11:28:44 |
| Message-ID: | CABOikdPL=TTsDtm1+a49+C=2XR3=W9pfAm-pWwdxq3EmeWdHMQ@mail.gmail.com |
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On Fri, Apr 12, 2013 at 4:29 PM, Andres Freund <andres(at)2ndquadrant(dot)com>wrote:
>
>
> I don't think that holds true at all. If you look at pg_stat_bgwriter in
> any remotely bugs cluster with a hot data set over shared_buffers you'll
> notice that a large percentage of writes will have been done by backends
> themselves.
>
Even if what you are saying it true, which I am sure is, the pages that the
backend is evicting mustn't be recently used by the LRU algorithm which
means that the WAL pertaining to the last change to the page in most
likelihood is already replicated, unless the replication is really lagging
much behind. Of course, if the standby is not able to keep pace with the
master in a realistic manner then we have a problem with the approach.
Thanks,
Pavan
--
Pavan Deolasee
http://www.linkedin.com/in/pavandeolasee
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