From: | Thom Brown <thom(at)linux(dot)com> |
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To: | George Barnett <gbarnett(at)atlassian(dot)com> |
Cc: | PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Patch to improve reliability of postgresql on linux nfs |
Date: | 2011-09-09 08:38:58 |
Message-ID: | CAA-aLv7-fWZuWYEch1ScZFFnktvRgfEjbAy4BFpw=uwN85Z=zA@mail.gmail.com |
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Lists: | pgsql-hackers |
On 9 September 2011 01:04, George Barnett <gbarnett(at)atlassian(dot)com> wrote:
> After looking through the code I found that when postgres calls write() it doesn't retry. In order to address the issue with the PANIC in the WAL writer I set the sync method to o_sync which solved the issue in that part of the code, however I was still seeing failures in other areas of the code (such as the FileWrite function). Following this, I spoke to an NFS guru who pointed out that writes under linux are not guaranteed to complete unless you open up O_SYNC or similar on the file handle.
Have you run the test with varying wal_sync_method values? On Linux
the default is fdatasync because historically Linux hasn't supported
O_DSYNC (a wal_sync_method value of open_datasync). But I believe as
of Kernel 2.6.33 it does support it. Have you tried modifying this
parameter in your tests? Are you even using Linux? (you haven't
specified)
--
Thom Brown
Twitter: @darkixion
IRC (freenode): dark_ixion
Registered Linux user: #516935
EnterpriseDB UK: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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