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Re: Block-level CRC checks

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Jonah H(dot) Harris" <jonah(dot)harris(at)gmail(dot)com>
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 15:36:44
Message-ID: 23211.1222875404@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
"Jonah H. Harris" <jonah(dot)harris(at)gmail(dot)com> writes:
> On Wed, Oct 1, 2008 at 10:27 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> Your optimism is showing ;-).  XLogInsert routinely shows up as a major
>> CPU hog in any update-intensive test, and AFAICT that's mostly from the
>> CRC calculation for WAL records.

> 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.

			regards, tom lane

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