Space need by a POD - Ephimeral vs Persistent space

Longhorn
1

Sorry if this is a trivial question, but not sure If I understand clearly how storage is used on Kubernetes world.

Basically, when I define a node working as worker, I assign to the node CPU, and Memory. Normally you do not see requeriments on space for the node, since it is assumed that space will be assigned later on to PODs using Persistent Volumes, etc…

However, if I not wrong, even on the case a Pod may need a not ephimeral storage (PVC) on Longhorn, for example, the pod may need also some space for being able to run (the ephimeral storage). How is that ephimeral storage sized and where is stored ? How much size of disk is suggested to get avaiable for nodes beside the PVCs ? Can you use also part of the size of the disk on the node for a Longhorm volume ?

All DOC I always read for nodes minimum requirement are talking about CPU and Mem, never about disk size, and I guess that disk is also consumed for ephimerl space, so will need some minimals there… How much ?

2

Have you checked the Kubernetes ephemeral volumes doc Ephemeral Volumes | Kubernetes yet?

It depends on what kind of ephemeral volume you want to use.
In general, the emtpyDir, configMap, downwardAPI, secret will not use the space on the disk.

I haven’t tried the CSI ephemeral volumes before, need some time to look at this one.