Consider the total RAM capacity of your servers. This is not nearly the quandary it once was, but it is still vital to plan carefully. If your server model accepts say at most 16 memory modules and your initial calculations are that 64 GB of RAM is what you need, resist the urge to save a few bucks on 4 GB DIMMs. Any future upgrades would require removing installed modules to make way for newer, larger DIMMs. Situations that could increase your RAM needs include:
- Adding more storage drives per server
- Swapping in larger storage drives for smaller
- Cluster expansion via additional servers may increase per-process memory requirements
- Future use of caching software
- Operating system or Ceph setting tweaks
- Conversion to a ...