In general, I fix the newgen size mostly to avoid the optimizer choosing something braindead in a pathological case. 50/50 is safe, but not optimal.
In general, you should have enough unallocated memory on the box to cover your working dataset (it'll get used by caches and memmaps). If you can, find a way to exploit data locality. I shoot for (number of cores * 1-4)-ish partitions per box depending on workload. Using bigger boxes is usually better, because you can avoid communication latency and variance that arises from having tons of boxes.
If you want to know more, you can email me at kyle@onemorecloud.com.
In general, you should have enough unallocated memory on the box to cover your working dataset (it'll get used by caches and memmaps). If you can, find a way to exploit data locality. I shoot for (number of cores * 1-4)-ish partitions per box depending on workload. Using bigger boxes is usually better, because you can avoid communication latency and variance that arises from having tons of boxes.
If you want to know more, you can email me at kyle@onemorecloud.com.