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Re: Block-level CRC checks

From: Simon Riggs <simon(at)2ndQuadrant(dot)com>
To: Bruce Momjian <bruce(at)momjian(dot)us>
Cc: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Aidan Van Dyk <aidan(at)highrise(dot)ca>, Alvaro Herrera <alvherre(at)commandprompt(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Block-level CRC checks
Date: 2009-12-01 13:08:17
Message-ID: 1259672897.13774.13163.camel@ebony (view raw or flat)
Thread:
Lists: pgsql-hackers
On Tue, 2009-12-01 at 07:42 -0500, Bruce Momjian wrote:
> Simon Riggs wrote:
> > On Tue, 2009-12-01 at 07:05 -0500, Bruce Momjian wrote:
> > 
> > > I assume torn pages are 99% of the reported problem, which are
> > > expected and are fixed, and bad hardware 1%, quite the opposite of your
> > > numbers above.
> > 
> > On what basis do you make that assumption?
> 
> Because we added full page write protection to fix the reported problem
> of torn pages, which we had on occasion;  now we don't.  Bad hardware
> reports are less frequent.

Bad hardware reports are infrequent because we lack a detection system
for them, which is the topic of this thread. It would be circular to
argue that as a case against.

It's also an argument that only effects crashes.

-- 
 Simon Riggs           www.2ndQuadrant.com


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