Re: Hardware/OS recommendations for large databases (

On Wed, 2005-11-16 at 11:47, Luke Lonergan wrote:
> Scott,

Some cutting for clarity... I agree on the OLTP versus OLAP
discussion.

> Here are the facts so far:
> * Postgres can only use 1 CPU on each query
> * Postgres I/O for sequential scan is CPU limited to 110-120
> MB/s on the fastest modern CPUs
> * Postgres disk-based sort speed is 1/10 or more slower than
> commercial databases and memory doesn’t improve it (much)

But PostgreSQL only spills to disk if the data set won't fit into the
amount of memory allocated by working_mem / sort_mem. And for most
Business analysis stuff, this can be quite large, and you can even crank
it up for a single query.

I've written reports that were horrifically slow, hitting the disk and
all, and I upped sort_mem to hundreds of megabytes until it fit into
memory, and suddenly, a slow query is running factors faster than
before.

Or did you mean something else by "disk base sort speed"???