I'm trying to figure out how to launch a web application in a Kubernetes cluster on AWS. Right now I'm not certain about a database. I can see that one can use raw block volumes, which are supposedly faster:
This mode is useful to provide a Pod the fastest possible way to access a volume, without any filesystem layer between the Pod and the volume.
https://kubernetes.io/docs/concepts/storage/persistent-volumes/
And they seem to be recommended particularly for databases:
There are some specialized applications that require direct access to a block device because, for example, the file system layer introduces unneeded overhead. The most common case is databases, which prefer to organize their data directly on the underlying storage.
https://kubernetes.io/blog/2019/03/07/raw-block-volume-support-to-beta/
By databases they supposedly mean PostgreSQL, MariaDB, Redis, whatever.
As such, I wonder if I should use raw block volumes for databases. Because on one hand they recommend it, but I didn't see an example. If so, should I create a custom database image to mount the device into the directory? Interestingly, Kubegres doesn't seem to be using block volumes:
My test yaml file:
apiVersion: apps/v1
kind: Deployment
metadata:
name: mydeployment
namespace: myns
spec:
replicas: 1
selector:
matchLabels:
app: myapp
template:
metadata:
labels:
app: myapp
spec:
containers:
- name: app
image: mariadb
env:
- name: MARIADB_ALLOW_EMPTY_ROOT_PASSWORD
value: '1'
volumeDevices:
- name: persistent-storage
devicePath: /dev/xvda
volumes:
- name: persistent-storage
persistentVolumeClaim:
claimName: ebs-claim
---
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
name: ebs-claim
namespace: myns
spec:
accessModes:
- ReadWriteOnce
storageClassName: gp2
volumeMode: Block
resources:
requests:
storage: 1Gi
