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Posted by Erland Sommarskog on 02/17/06 10:20
Erland Sommarskog (esquel@sommarskog.se) writes:
> My gut feeling is that torn-page detection should be such a
> performance hog, but that is just a feeling. I have never played
> with it, so I've posted a question to my MVP mates, to see if thety
> have anything to add.
I got some answers. A MS developer told me that updates should not be
affected at all, as they don't look at the checksums then. The
Checkpoint/Lazy writer processes would be affected, but user threads
should not notice this. My own reaction is that if you are seeing
degradation with torn-page detection, it may be a token of the same
problem that causes your backups to hog the machine.
Another MVP told me this about torn pages:
One thing I think that should be mentioned regardless of the
performance discussion is that he/she needs to not think that since
they have write cache and a Raid that they are safe from torn page's.
I had a system that had a raid backend with cache and all sorts of
"redundancy" built into it and it took one admin moving cables on the san
switch to mess things up and cause torn pages. I'm thankful for the
detection since I didn't lose the whole database or cause more issues and
was able to fix it. So it might be good to mention that just because you
have Hardware doesn't mean your always safe. :)
--
Erland Sommarskog, SQL Server MVP, esquel@sommarskog.se
Books Online for SQL Server 2005 at
http://www.microsoft.com/technet/prodtechnol/sql/2005/downloads/books.mspx
Books Online for SQL Server 2000 at
http://www.microsoft.com/sql/prodinfo/previousversions/books.mspx
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