Re: Slow count(*) again...

Samuel Gendler wrote:
> I spent some time going through the various tuning docs on the wiki
> whie bringing some new hardware up and I can't remember seeing any
> discussion of tweaking read-ahead at all in the normal
> performance-tuning references.  Do you have any documentation of the
> kinds of tweaking you have done and its effects on different types of
> workloads?

Much of my recent research has gone into the book you'll see plugged
below rather than the wiki.  The basics of read-ahead tuning is that you
can see it increase bonnie++ sequential read results when you increase
it, to a point.  Get to that point and stop and you should be in good shape.

--
Greg Smith, 2ndQuadrant US greg@2ndQuadrant.com Baltimore, MD
PostgreSQL Training, Services and Support  www.2ndQuadrant.us
Author, "PostgreSQL 9.0 High Performance"    Pre-ordering at:
https://www.packtpub.com/postgresql-9-0-high-performance/book