All pods are assigned a Quality of Service (QoS). These are 3 levels of priority pods are assigned within a node.
The levels are as following:
1) Guaranteed: High Priority
2) Burstable: Medium Priority
3) BestEffort: Low Priority
It is a way of telling the kubelet what your priorities are on a certain node if resources need to be reclaimed. This great GIF below by Anvesh Muppeda explains it.
If resources need to be freed, firstly pods with Best Effort QoS will be evicted, then those with Burstable, and finally those with Guaranteed.
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