Thanks that certainly agrees with much of what we've found by trial and error.
Considering our default data cache
IOBufferSize | AllocatedKB | PagesTouched | PagesRead | CacheName | |
16k | 31744000 | 7,312,309 | 98,242,928 | default data cache | 23.04 |
128k | 10240000 | 479,160 | 71,024,280 | default data cache | 4.68 |
The PagesTouched/Allocated shows the 16k pool a lot more than the 128k and year the pages read from each cache is very similar 98m vs 71m.
So I guess we're reading a lot of pages from the large IO pool but very few of them.
Thanks again