On 10/3/05 2:43 PM, "Hannu Krosing" <[EMAIL PROTECTED]> wrote:

> Just FYI, I run a count(*) on a 15.6GB table on a lightly loaded db and
> it run in 163 sec. (Dual opteron 2.6GHz, 6GB RAM, 6 x 74GB 15k  disks in
> RAID10, reiserfs). A little less than 100MB sec.

This confirms our findings - sequential scan is CPU limited at about 120MB/s
per single threaded executor.  This is too slow for fast file systems like
we're discussing here.

Bizgres MPP gets 250MB/s by running multiple scanners, but we still chew up
unnecessary amounts of CPU.
> After this I ran count(*) over a 2.4GB file from another tablespace on
> another device (4x142GB 10k disks in RAID10) and it run 22.5 sec on
> first run and 12.5 on second.

You're getting caching effects here.

- Luke

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