In our project we are currently using ignite 2.7.6 with native persistence disabled and java 11. At the moment we are not using the on-heap feature, i.e. all our data lives in off-heap. However in order to gain performance we are thinking about activating on-heap. While there are already quite many questions/answers on that topic in this forum we are still missing some points. I would like to use the following scenario for our questions: Say we have one ignite-server-instance living on a *kubernetes-pod of 32 GiB memory request/limit size* with the following "hypothetical" configuration:
- JVM options exactly as described here https://apacheignite.readme.io/docs/jvm-and-system-tuning, i.e. in particular *10 GB heap fixed*. - Off-heap is limited to 15 GiB by adjusting the default region with *initSize = maxSize = 15 GiB*. No more data regions are defined. Before doing anything with our ignite-server-instance we *initially fill its off-heap with 10 GiB* of data and this will be the only data that it will receive. What happens when we set *org.apache.ignite.configuration.CacheConfiguration.setOnheapCacheEnabled(true) in each data configuration and for now use no eviction policies* in particular during loading these 10 GB of data? More precisely: 1. As it is emphasised several times in this forum the data will still be be loaded into off-heap. But will it immediately also be loaded into heap, i.e. during the loading procedure each data point gets replicated simultaneously to heap resulting in two copies of the same data one in off-heap and one on heap after the procedure is finished? 2. ... Or will a given data point only be replicated to heap when ever it is being used, i.e. during computations? 3. Lets furthermore assume that our overall configuration was stable before switching to on-heap. In order to guarantee that it will do so afterwards would we need to increase the heap size by roughly 10 GB to 20 GB and therefore also our pod size to roughly 42 GiB? That would imply that using on-heap always goes hand in hand with increasing memory resources. 4. Obviously in this example we did not define any eviction-policy to control the on-heap cache size. However this is indeed intended here because we would like each data point to be quickly available living also in heap. Is this a useful approach (i.e. replicating the whole off-heap also in heap) in order to reach the overall goal namely better performance? It feels like this approach would counteract the change to the off-heap model from ignite 2.x.x onwards in terms of GC impacts and so on. Is this correct? Please let me know if you need more detailed informations about the configurations/settings we use. Thanks in advance! Vincent -- Sent from: http://apache-ignite-users.70518.x6.nabble.com/
