According to the configuration reference, memory-size “Cannot be reduced by more than 50% of previously set value.” Can I reduce it more than 50% as long I do it in stages? Or is this an architectural limit?
I’m trying to convert a 12-machine cluster of r3.4xlarge machines (122GB RAM, 10% memory usage) to a similarly sized cluster of i3.large machines (15GB RAM, expected 80% memory usage). I’d like to add the new machines to the existing cluster, and then spin down the old ones, but I’ll have to reduce memory-size first.
So the plan would be:
- Increase memory HWM to 80%
- Reduce memory-size, in stages, to 11-12GB. [Will this be possible?]
- Add 13 new i3.large nodes
- Remove r3.4xlarge nodes one-by-one, waiting for migrations to complete between each
Some considerations that have led to the above plan:
- i3.large instances are far cheaper than r3.4xlarge.
- Any downtime at all on this cluster is extremely expensive
- We don’t have the Enterprise package, so a backup + restore + XDR is not an option
- Simple backup + restore involves too much downtime