Re: Script to compute random page cost

Bruce-

With the change in the script that I mentioned to you off-list (which I
believe just pointed it at our "real world" data), I got the following
results with 6 successive runs on each of our two development platforms:

(We're running PGSQL 7.2.1 on Debian Linux 2.4)

System 1:
1.2 GHz Athlon Processor, 512MB RAM, Database on IDE hard drive
random_page_cost = 0.857143
random_page_cost = 0.809524
random_page_cost = 0.809524
random_page_cost = 0.809524
random_page_cost = 0.857143
random_page_cost = 0.884615

System 2:
Dual 1.2Ghz Athlon MP Processors, SMP enabled, 1 GB RAM, Database on Ultra
SCSI RAID 5 with Hardware controller.
random_page_cost = 0.894737
random_page_cost = 0.842105
random_page_cost = 0.894737
random_page_cost = 0.894737
random_page_cost = 0.842105
random_page_cost = 0.894737

I was surprised that the SCSI RAID drive is generally slower than IDE, but
the values are in line with the results that others have been getting.

-Nick

> -----Original Message-----
> From: pgsql-hackers-owner(at)postgresql(dot)org
> [mailto:pgsql-hackers-owner(at)postgresql(dot)org]On Behalf Of Bruce Momjian
> Sent: Monday, September 09, 2002 1:14 AM
> To: PostgreSQL-development
> Subject: Re: [HACKERS] Script to compute random page cost
>
>
>
> OK, turns out that the loop for sequential scan ran fewer times and was
> skewing the numbers. I have a new version at:
>
> ftp://candle.pha.pa.us/pub/postgresql/randcost
>
> I get _much_ lower numbers now for random_page_cost.