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Re: Block-level CRC checks

From: "Jonah H(dot) Harris" <jonah(dot)harris(at)gmail(dot)com>
To: "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql(at)mohawksoft(dot)com, "Hannu Krosing" <hannu(at)2ndquadrant(dot)com>, Decibel! <decibel(at)decibel(dot)org>, "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 15:54:17
Message-ID: 36e682920810010854l5a4c4910u4a944ee447f4c343@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On Wed, Oct 1, 2008 at 11:36 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> I probably wouldn't compare checksumming *every* WAL record to a
>> single block-level checksum.
>
> No, not at all.  Block-level checksums would be an order of magnitude
> more expensive: they're on bigger chunks of data and they'd be done more
> often.

That's debatable and would be dependent on cache and the workload.

In our case however, because shared buffers doesn't scale, we would
end up doing a lot more block-level checksums than the other vendors
just pushing the block to/from the OS cache.

-- 
Jonah H. Harris, Senior DBA
myYearbook.com

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