Imported from Medium: https://medium.com/@aruny/understanding-redis-memory-requirement-8fdb05da48a7
RDB on, server stopped taking new connection since RDB was failing after 4.61GB of RAM data, the rss/used memory ratio hit 0.5. means half of the data was swapped by OS. RDB failed because it uses copy-on-write which requires equal amount of RAM to actual changed data.
# Memory
used_memory:9917597920
used_memory_human:9.24G
used_memory_rss:4957216768
used_memory_peak:9917597920
used_memory_peak_human:9.24G
used_memory_lua:36864
mem_fragmentation_ratio:0.50
mem_allocator:jemalloc-3.6.0
With RDB off
# Memory
used_memory:12061875128
used_memory_human:11.23G
used_memory_rss:7251791872
used_memory_peak:12061875128
used_memory_peak_human:11.23G
used_memory_lua:36864
mem_fragmentation_ratio:0.60 (rss/used)
mem_allocator:jemalloc-3.6.0