Michael,
> Well, you don't have to spend *quite* that much to get a decent storage
> array. :)
Yes, I'm just pointing out that it's only the extreme cases which are
clear-cut. Middle cases are a lot harder to define. For example, we've
found that on DBT2 running of a 14-drive JBOD, seperating off WAL boosts
performance about 8% to 14%. On DBT3 (DSS) seperate WAL (and seperate
tablespaces) helps considerably during data load,but not otherwise. So it
all depends.
> That's a different creature from
> a data mining app that might really benefit from having additional
> spindles to accelerate read performance from indices much larger than
> RAM.
Yes, although the data mining app benefits from the special xlog disk
during ETL. So it's a tradeoff.
> At any rate, this just underscores the need for testing a
> particular workload on particular hardware
Yes, absolutely.
--
--Josh
Josh Berkus
Aglio Database Solutions
San Francisco
