Hi Mark,
> lineitem has 1535724 pages (11997 MB)
>
> Shared Buffers Elapsed IO rate (from vmstat)
> -------------- ------- ---------------------
> 400MB 101 s 122 MB/s
>
> 2MB 100 s
> 1MB 97 s
> 768KB 93 s
> 512KB 86 s
> 256KB 77 s
> 128KB 74 s 166 MB/s
>
> I've added the observed IO rate for the two extreme cases
> (the rest can be pretty much deduced via interpolation).
>
> Note that the system will do about 220 MB/s with the now
> (in)famous dd test, so we have a bit of headroom (not too bad
> for a PIII).
What's really interesting: try this with a table that fits into I/O
cache (say half your system memory), and run VACUUM on the table. That
way the effect will stand out more dramatically.
- Luke
