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Re: Page Checksums + Double Writes

From: "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
To: "Jeff Janes" <jeff(dot)janes(at)gmail(dot)com>, "Robert Haas" <robertmhaas(at)gmail(dot)com>
Cc: "Simon Riggs" <simon(at)2ndquadrant(dot)com>, <alvherre(at)commandprompt(dot)com>,<david(at)fetter(dot)org>, <pgsql-hackers(at)postgresql(dot)org>, <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Subject: Re: Page Checksums + Double Writes
Date: 2011-12-23 20:23:54
Message-ID: 4EF48EFA02000025000440CC@gw.wicourts.gov (view raw or flat)
Thread:
Lists: pgsql-hackers
Jeff Janes <jeff(dot)janes(at)gmail(dot)com> wrote:
 
> Could we get some major OLTP users to post their CLOG for
> analysis?  I wouldn't think there would be much
> security/propietary issues with CLOG data.
 
FWIW, I got the raw numbers to do my quick check using this Ruby
script (put together for me by Peter Brant).  If it is of any use to
anyone else, feel free to use it and/or post any enhanced versions
of it.
 
#!/usr/bin/env ruby

Dir.glob("*") do |file_name|
  contents = File.read(file_name)
  total = 
    contents.enum_for(:each_byte).enum_for(:each_slice,
256).inject(0) do |count, chunk|
      if chunk.all? { |b| b == 0x55 }
        count + 1
      else
        count
      end
    end
  printf "%s %d\n", file_name, total
end
 
-Kevin

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