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Re: What's the best hardver for PostgreSQL 8.1? - Mailing list pgsql-performance

From William Yu
Subject Re: What's the best hardver for PostgreSQL 8.1?
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Msg-id docq5v$24ea$1@news.hub.org
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In response to Re: What's the best hardver for PostgreSQL 8.1?  (Juan Casero <caseroj@comcast.net>)
Responses Re: What's the best hardver for PostgreSQL 8.1?
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Juan Casero wrote:
> Can you elaborate on the reasons the opteron is better than the Xeon when it
> comes to disk io?   I have a PostgreSQL 7.4.8 box running a DSS.   One of our

Opterons have 64-bit IOMMU -- Xeons don't. That means in 64-bit mode,
transfers to > 4GB, the OS must allocated the memory < 4GB, DMA to that
block and then the CPU must do extra work in copying the memory to >
4GB. Versus on the Opteron, it's done by the IO adaptor using DMA in the
background.

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