Re: More memory, or more processors

Neil, Truby wrote: > > We are running a heavy-duty aplication under Informix OnLine 7.13 os a Sun Sparc > 20 with 2 x 75MHz processors and 160M of physical memory. > > Budget has been set aside to purchase a hardware upgrade, viz an Ultra 4000. > The specification was to have been 4x250Mhz processors and 1G of memory. > > A consultant has done a sizing exercise on our current configuration and, as a > result, we have upgraded it to 384M of memory. The server is showing > significantly lower page scan rates, so I think this has been of benefit. > > The consultant is now recommending that we configure with 1.5G of memory and > just 2x250MHz processors. > > Does anyone have any experience of which OnLine is likely to better utilise; > 0.5G of extra memory, or 2 additional processors? If you want to individual, simpler, queries to execute faster go for more memory. To better support more users or more complex queries go for more CPU. Also look at how much memory you are actually using. It will do you no good to add the extra 1/2GB if Informix is only using 500MB of shared memory and other processes only another 300MB if Informix is using raw devices that still leaves 200MB for UNIX buffer cache which is 20% of RAM and usually plenty. So unless Informix's cache hit ratio is low and you can benefit from more cache or you frequently add dynamic memory segments, go for the extra CPUs. Art S. Kagel