Re: Large tables (was: RAID 0 not as fast as

From: Ron Mayer <rm_pg(at)cheapcomplexdevices(dot)com>
To: Luke Lonergan <llonergan(at)greenplum(dot)com>
Subject: Re: Large tables (was: RAID 0 not as fast as
Date: 2006-09-24 13:29:50
Message-ID: 4516884E.6070308@cheapcomplexdevices.com
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Luke Lonergan wrote:
>
> I think the topic is similar to "cache bypass", used in cache capable vector
> processors (Cray, Convex, Multiflow, etc) in the 90's. When you are
> scanning through something larger than the cache, it should be marked
> "non-cacheable" and bypass caching altogether. This avoids a copy, and
> keeps the cache available for things that can benefit from it.

And 'course some file systems do this automatically when they
detect a sequential scan[1] though it can have unexpected (to some)
negative side effects[2]. For file systems that support freebehind
as a configurable parameter, it might be easier to experiment with
the idea there.

[1] http://www.ediaudit.com/doc_sol10/Solaris_10_Doc/common/SUNWaadm/reloc/sun_docs/C/solaris_10/SUNWaadm/SOLTUNEPARAMREF/p18.html
[2] http://bugs.opensolaris.org/bugdatabase/view_bug.do?bug_id=6207772

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