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Re: Block-level CRC checks

From: "Albe Laurenz" <laurenz(dot)albe(at)wien(dot)gv(dot)at>
To: "Jonah H(dot) Harris *EXTERN*" <jonah(dot)harris(at)gmail(dot)com>,"Joshua Drake" <jd(at)commandprompt(dot)com>
Cc: "Alvaro Herrera" <alvherre(at)commandprompt(dot)com>,"Pg Hackers" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Block-level CRC checks
Date: 2008-10-01 07:01:08
Message-ID: D960CB61B694CF459DCFB4B0128514C202901A88@exadv11.host.magwien.gv.at (view raw or flat)
Thread:
Lists: pgsql-hackers
Jonah H. Harris wrote:
>>>> I'd like to submit this for 8.4, but I want to ensure that -hackers
>>>> at large approve of this feature before starting serious coding.
>>>
>>> IMHO, this is a functionality that should be enabled by default (as it
>>> is on most other RDBMS).  It would've prevented severe corruption in
>>
>> What other RDMS have it enabled by default?
> 
> Oracle and (I belive) SQL Server >= 2005

References:
http://download-uk.oracle.com/docs/cd/B19306_01/server.102/b14237/initparams040.htm#CHDDCEIC
http://download.oracle.com/docs/cd/B28359_01/server.111/b28320/initparams046.htm#sthref130

Oracle claims that it introduces only 1% to 2% overhead.

Actually I suggested the same feature for 8.3:
http://archives.postgresql.org/pgsql-hackers/2007-08/msg01003.php

It was eventually rejected because the majority felt that it
would be a small benefit (only detects disk corruption and not
software bugs) that would not justify the overhead and the
additional code.

Incidently, Oracle also has a parameter DB_BLOCK_CHECKING
that checks blocks for logical consistency. This is OFF by default,
but Oracle recommends that you activate it if you can live with
the performance impact.

Yours,
Laurenz Albe

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