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Re: Block-level CRC checks

From: Alvaro Herrera <alvherre(at)commandprompt(dot)com>
To: Robert Treat <xzilla(at)users(dot)sourceforge(dot)net>
Cc: pgsql-hackers(at)postgresql(dot)org, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql(at)mohawksoft(dot)com, Hannu Krosing <hannu(at)2ndquadrant(dot)com>, Decibel! <decibel(at)decibel(dot)org>
Subject: Re: Block-level CRC checks
Date: 2008-10-02 20:13:49
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers
Robert Treat wrote:
> On Wednesday 01 October 2008 10:27:52 Tom Lane 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.
> Yeah... for those who run on filesystems that do checksumming for you, I'd bet 
> they'd much rather see time spent in turning that off rather than 
> checksumming everything else.  (just guessing) 

I don't think it can be turned off, because ISTR a failed checksum is
used to detect end of the WAL stream to be recovered.

Alvaro Herrera                      
The PostgreSQL Company - Command Prompt, Inc.

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