In my most recent 101 post on ReadWriteMany volumes, I shared an example whereby we created an NFS server in a Pod which automatically exported a File Share. We then mounted the File Share to multiple NFS client Pods deployed in the same namespace. We saw how multiple Pods were able to write to the same ReadWriteMany volume, which was the purpose of the exercise. I received a few questions on the back on that post relating to the use of Services. In particular, could an external NFS client, even one outside of the K8s cluster, access a volume from…
Over the last number of posts, we have spent a lot of time looking at persistent volumes (PVs) instantiated on some vSphere back-end block storage. These PVs were always ReadWriteOnce, meaning they could only be accessed by a single Pod at any one time. In this post, we will take a look at how to create a ReadWriteMany volume, based on an NFS share, which can be accessed by multiple Pods. To begin, we will use an NFS server image running in a Pod, and show how to mount the exported file share to another Pod, simply to get the…
We have looked at quite a few scenarios when Kubernetes is running on vSphere, and what that means for storage. We looked at PVs, PVC, PODs, Storage Classes, Deployments and ReplicaSets, and most recently we looked at StatefulSets. In a few of the posts we looked at some controlled failures, for example, when we deleted a Pod from a Deployment or from a StatefulSet. In this post, I wanted to look a bit closer at an uncontrolled failure, say when a node crashes. However, before getting into this in too much details, it is worth highlighting a few of the…
In my last post we looked at creating a highly available application that used multiple Pods in Kubernetes with Deployments and ReplicaSets. However, this was only focused on Pods. In this post, we will look at another way of creating highly available applications through the use of StatefulSets. The first question you will probably have is what is the difference between a Deployment (with ReplicaSets) and a StatefulSet. From a high level perspective, conceptually we can consider that the major difference is that a Deployment is involved in maintaining the desired number of Pods available for an application, whereas a…
In the first 101 post, we talked about persistent volumes (PVs), persistent volumes claims (PVCs) and PODs (a group of one or more containers). In particular, we saw how with Kubernetes on vSphere, a persistent volume is essentially a VMDK (virtual machine disk) on a datastore. In that first post, we created a static VMDK on a vSAN datastore, then built manifest files (in our case YAML) for a PV, a persistent volume claim (PVC) and finally a Pod, and showed how to map that static preexisting VMDK directly to the Pod, so that it could be mounted. We saw…
I’ve just returned from KubeCon 2019 in Barcelona, and was surprised to see such a keen interest in how Kubernetes consumed infrastructure related resources, especially storage. Although I have been writing about a lot of Kubernetes related items recently, I wanted to put together a primer on some storage concepts that might be useful as a stepping stone or even on-boarding process to some of you who are quite new to Kubernetes. I am going to talk about this from the point of view of vSphere and vSphere storage. Thus I will try to map vSphere storage constructs such as…
If you’ve been following my posts for the last week or so, you’ll have noticed my write-ups on Velero backups and restores using the new release candidate (RC). I also did a recent write-up on Portworx volumes and snapshots. In this post, I’ll bring them both together, and show you how Velero and Portworx are integrated to allow backups and restores of container applications using Portworx volumes. However, first, let’s take a step back. As was highlighted to me recently, all of this is very new to a lot of people, so let’s spend a little time setting the context.…