efk persistant storage

[McSlow]

Is this a BUG REPORT or FEATURE REQUEST? (choose one):
Feature Request

Environment:

• Cloud provider or hardware configuration:
  local vpshere

Currently, if the EFK stack is activated, it seems that it uses a volume called es-persistent-storage
which is hardwired and an emptyDir:
https://github.com/kubernetes-incubator/kubespray/blob/69ea28e1878b27ef5622a45aed0539347d66f893/roles/kubernetes-apps/efk/elasticsearch/templates/elasticsearch-deployment.yml.j2#L51

emptyDir is possibly not what you want if your cluster allows pvc's.
So an option that allows the usage of a (pvc) storage class would be nice -especially when your nodes do not have a lot of disk space (but do have a storage system with lots of space).

Perhaps I can provide a PR.

Anything else do we need to know:

[McSlow]

btw: found this out because elastic completely blew up our node's disk space, triggering imageFS pressue which in consequence killed the elastic container :)

[Atoms]

@McSlow the problem is if you do not add volume provisioning then you are not able to add pvc, so it should check lot of things before that :( but yes if you are willing to make PR please do, gladly will review.

[desaintmartin]

Basically, a simple home-made version is here : wiremind@f9fc6be

It does not contain all the checks, of course, so I'm not (yet? No time right now) making a PR.

[Atoms]

We are removing EFK Stack from kubespray:
#3352