Containarized Gluster Storage in Kubernetes by Saravanakumar Arumugam, Red Hat

1. Gluster Storage in Kubernetes
Saravanakumar Arumugam
25 August 2018
Joint meetup by:
Docker and Kubernetes community,
Bangalore

2. 2
Agenda
● GlusterFS Storage
● Kubernetes Storage Concepts
● GlusterFS in Kubernetes
● Demo

3. ● Scale-out distributed storage system.
● Aggregates storage exports over network interconnects to provide
an unified namespace.
● Layered on disk file systems that support extended attributes.
● Provides file, object and block interfaces for data access.
GlusterFS

4. GlusterFS Demo

5. 5
Openshift (Kubernetes)
OpenShift - Enterprise Kubernetes for Developers
Openshift Container Platform(OCP) is Red Hat’s PaaS offering that offers customers
a full stack platform for creating/maintaining micro-services.
Upstream: https://github.com/openshift/origin

6. PODPOD
containers are wrapped in pods which are
units of deployment and management
6
CONTAINER CONTAINERCONTAINER
IP: 10.1.0.11 IP: 10.1.0.55

7. pods configuration is defined
in a deployment
7
image name
replicas
labels
cpu
memory
storage
POD
CONTAINER
POD
CONTAINER
POD
CONTAINER
DEPLOYMENT

8. POD
services provide internal load-balancing and
service discovery across pods
8
CONTAINER
POD
CONTAINER
POD
CONTAINER
BACKEND SERVICE
POD
CONTAINER
role: backend
role: backendrole: backendrole: backendrole: frontend

9. POD
apps can talk to each other via services
9
CONTAINER
POD
CONTAINER
POD
CONTAINER
BACKEND SERVICE
POD
CONTAINER
role: backend
role: backendrole: backendrole: backendrole: frontend
Invoke
Backend API

10. POD
routes add services to the external load-balancer
and provide readable urls for the app
10
CONTAINER
POD
CONTAINER
POD
CONTAINER
BACKEND SERVICE
ROUTE
app-prod.mycompany.com
> curl http://app-prod.mycompany.com

11. projects isolate apps across environments,
teams, groups and departments
11
POD
C
POD
C
POD
C
PAYMENT DEV
POD
C
POD
C
POD
C
PAYMENT PROD
POD
C
POD
C
POD
C
CATALOG
POD
C
POD
C
POD
C
INVENTORY
❌
❌❌

12. ● What are Containers and images, and how are they different
○ Image = Binary Artifact
○ Container = Running Instantiation of an image
● What are Pods, Services, Route
○ Pods are the baseline unit, used in defining an application or process
○ Services are discovery/routing objects used to interact with pods/containers
○ Routes are for external world to access the pods.
● What is a Project/Namespace
○ A logical grouping / workspace for resources
○ Aso acts as an isolation boundary for networking and permissions
Recap..

13. Containers are ephemeral by nature, but many applications
require storage that is persistent beyond the life cycles of the
application containers.
Use cases:
● persistent storage for application containers
● Registry
Storage in containers

14. ● StorageClass
● PVC - PersistentVolumeClaim
● PV - PersistentVolume
Some more at background:
● Provisioner
● Mount plugin
Storage concepts in Kubernetes

15. ● created by admin
● describes the storage
● references a (dynamic) provisioner
Example:
https://github.com/gluster/gluster-kubernetes/blob/master/deploy/kube-templates/gluster-s3-s
torageclass.yaml#L2
StorageClass

16. - created by user
- references Storageclass
- says which provisioner to use ( answer: glusterfs)
Example:
https://github.com/gluster/gluster-kubernetes/blob/423b0c4d50e299e8f
429a5a820ba0389e365d005/deploy/ocp-templates/gluster-s3-pvcs.ya
ml#L5
PersistentVolumeClaim - PVC

17. ReadWriteOnce RWO
The volume can be mounted as read-write by a single node.
ReadOnlyMany ROX
The volume can be mounted read-only by many nodes.
ReadWriteMany RWX
The volume can be mounted as read-write by many nodes.
Access modes in PVC

18. ● when user creates a PVC(with storageclass referenced) PV is
created.
● PV is the actual volume to be mounted in the application.
● PV is bound to PVC.
❖ Creating PVC automatically creates PV.
❖ The PVC controls the lifecycle of the storage, not the PV.
PersistentVolume - PV

19. Workflow
PVC
(Size)
PV
User
Admin
StorageClass

20. The workflow for dynamically provisioning storage is as follows:
1. An administrator sets up some storage, then defines a storage class
(SC) that describes the storage.
2. A user creates a persistent volume claim (PVC) to request some
storage of a given size, access type, and SC
3. A persistent volume (PV) is dynamically created of the requested size
on some storage that matches the SC.
4. The matched PV is then bound to the PVC and can be used by the
user in pods. The data in the PV persists beyond the lifecycle of the pod.
When the PVC is deleted, the PV is released.
Lifecycle of Volume creation

21. Demo

22. Gluster-Kubernetes
https://github.com/gluster/gluster-kubernetes
Gluster containers
https://github.com/gluster/gluster-containers
GlusterFS
https://github.com/gluster/glusterfs
Credits to : GlusterFS and OpenShift Community
References:

23. Thank you!
https://github.com/SaravanaStorageNetwork