<p>I was told by a more experienced DevOps person, that resource(CPU and Memory) limit and request would be nicer to be closer for scheduling pods. </p>

<p>Intuitively I can image less scaling up and down would require less calculation power for K8s? or can someone explain it in more detail?</p>

Holm
<p>The resource requests and limits do two fundamentally different things.  The Kubernetes scheduler places a pod on a node based only on the sum of the resource requests: if the node has 8 GB of RAM, and the pods currently scheduled on that node requested 7 GB of RAM, then a new pod that requests 512 MB will fit there.  The limits control how much resource the pod is actually allowed to use, with it getting CPU-throttled or OOM-killed if it uses too much.</p>

<p>In practice many workloads can be "bursty".  Something might require 2 GB of RAM under peak load, but far less than that when just sitting idle.  It doesn't necessarily make sense to provision enough hardware to run everything at peak load, but then to have it sit idle most of the time.</p>

<p>If the resource requests and limits are far apart then you can "fit" more pods on the same node.  But, if the system as a whole starts being busy, you can wind up with many pods that are all using above their resource request, and actually use more memory than the node has, without any individual pod being above its limit.</p>

<p>Consider a node with 8 GB of RAM, and pods with 512 MB RAM resource requests and 2 GB limits.  16 of these pods "fit".  But if each pod wants to use 1 GB RAM (allowed by the resource limits) that's more total memory than the node has, and you'll start getting arbitrary OOM-kills.  If the pods request 1 GB RAM instead, only 8 will "fit" and you'll need twice the hardware to run them at all, but in this scenario the cluster will run happily.</p>

<p>One strategy for dealing with this in a cloud environment is what your ops team is asking, make the resource requests and limits be very close to each other.  If a node fills up, an autoscaler will automatically request another node from the cloud.  Scaling down is a little trickier.  But this approach avoids problems where things die randomly because the Kubernetes nodes are overcommitted, at the cost of needing more hardware for the idle state.</p>
