Detail
The system_free_mem_pct is showing 20% but memory_used_bytes is only 22G for a system with 62G total memory.Answer
The primary reason is that the allocated shared memory (shmem) is not released after allocation.
Each Aerospike cluster has 4096 master partitions per namespace. So consider a 20-node cluster, each node typically owns around 200 master partitions (4096/20). Whenever a node departs or a split-brain scenario occurs, partition ownership undergoes reassignment. Rebalancing results in nodes assuming ownership of new partitions, leading to an expansion of shared memory (shmem). The asd process expands in 1GB increments by default (index-stage-size). Although primary indexes associated with old partitions are dropped during migrations, the allocated shmem persists for future and will not be released. A cold-start can be used to recover the allocated shmem.