Re: Perfomance Tuning

On Tue, 12 Aug 2003, Christopher Browne wrote:

> Are you _certain_ that's still true? Have you a metric that shows
> Informix being 10x faster on a modern system? That would be quite
> surprising...
>

We were forced (for budget reason) to switch from raw disk to cooked files
on our informix db. We took a huge hit - about 5-6x slower. Granted part
of that was because informix takes number of spindles, etc into account
when generating query plans and the fact running UPDATE STATISTICS (think
Vacuum analyze) on the version we run locks the table exclusively. And it
is unacceptable to have our "main table" unavailable for hours and hours
while the update runs. (For the record: its a 8cpu sun e4500 running
sol2.6. The raw disks were on a hitachi fibre array and the cooked files
were on a raid5 (scsi). Forget how many spindles in the raid.
There were 20 raw disks)

Informix, etc. have spent a lot of time and money working on it.
They also have the advantage of having many paid fulltime
developers who are doing this for a job, not as a weekend hobby
(Compared to the what? 2-3 full time PG developers).

The other advantage (which I hinted to above) with raw disks is being able
to optimize queries to take advantage of it. Informix is multithreaded
and it will spawn off multiple "readers" to do say, a seq scan (and merge
the results at the end).

So if you have a table across say, 3 disks and you need to do a seq scan
it will spawn three readers to do the read. Result: nice and fast (Yes, It
may not always spawn the three readers, only when it thinks it will be a
good thing to do)

I think for PG the effort would be much better spent on other features...
like replication and whatnot.

--
Jeff Trout <jeff(at)jefftrout(dot)com>
http://www.jefftrout.com/
http://www.stuarthamm.net/