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FAQ - What is the consequence of increasing high-water-memory-pct ?
Detail
There are a number of tunables within Aerospike to manage node resource usage. One of these is high-water-memory-pct which defines the threshold of memory at which eviction will start. What is the consequence of raising this past default levels?
Answer
If appropriate to the use case, there is no issue with increasing high-water-memory-pct, however the effects should be understood. When setting high-water-memory-pct, the key thing to bear in mind is that this is not a hard limit on memory usage, it is the point at which evictions due to memory usage start. It is quite possible for the high-water-memory-pct to be breached, for evictions to start and for memory usage to continue to climb past 100% of what has been allotted for the namespace. As evictions can be relatively slow (dependent on various tuning factors) it is not inconceivable that the system could run out of memory while evictions are happening.
With this in mind, high-water-memory-pct should be set with sufficient headroom to ensure that the system does not run out of memory in the event of it being breached.
Notes
The following article discusses various Aerospike defaults and the reasons for their value:
The article linked below deals with high-water-disk-pctand how this is related to defragmentation:
Keywords
MEMORY HIGH WATER MARK THRESHOLD OOM EVICTIONS
Timestamp
02/21/2019