1. storage volumes Overview
Because the pod is a life cycle, pod a restart, which the data is gone, so we need persistent data stored in k8s, the storage volume does not belong to the container, but to the pod, that is to say in the same pod the container may share a storage volume, the storage volume can be a directory on the host, or may be mounted on an external host apparatus.
Storage volume types:
emptyDIR storage volume : pod a restart, delete storage volumes, called emptyDir storage volumes, are generally used as temporary buffer space or relationships;
hostPath storage volume : directory on the host as a storage volume, this is not the true sense of the realized data persistence;
SAN (iscsi) or NAS (nfs, cifs): network storage devices;
Distributed storage: ceph, glusterfs, cephfs, rbd
Cloud Storage: Amazon EBS, Azure Disk, Ali cloud, critical data must be backed up off-site
a.emptyDIR storage volumes
vim subtest / sub-volume demo.yaml
apiVersion: v1
kind: Pod
metadata:
name: pod-demo
namespace: default
labels:
app: myapp
tier: frontend
spec:
containers:
- name: myapp
image: ikubernetes/myapp:v2
imagePullPolicy: IfNotPresent
ports:
- name: http
containerPort: 80
volumeMounts:
- name: html
mountPath: /usr/share/nginx/html
- name: busybox
image: busybox:latest
imagePullPolicy: IfNotPresent
volumeMounts:
- name: html
mountPath: /data/
command: ["/bin/sh"]
args: ["-c","while true;do echo $(date) >> /data/index.html; sleep 10;done"]
volumes:
- name: html
emptyDir: {}
volumeMounts: the storage volume of which linked to the pod which directory
emptyDir: not setting means that no limit on the two options under this parameter
b.hostPath: Use as a directory on host storage volume
kubectl explain pods.spec.volumes.hostPath.type
DirectoryOrCreate: To mount path is a directory, create a directory does not exist;
Directory: must realize there is a directory on the host, if there is no error;
FileOrCreate: represents the mount that file, if there is no creation;
File: pledged to mount the file must already exist, otherwise an error.
cat pod-hostpath-vol.yaml
apiVersion: v1
kind: Pod
metadata:
name: pod-vol-hostpath
namespace: default
spec:
containers:
- name: myapp
image: ikubernetes/myapp:v2
volumeMounts:
- name: html
mountPath: /usr/share/nginx/html/
volumes:
- name: html
hostPath:
path: /data/pod/volume1
type: DirectoryOrCreate
hostPath: directory on the host.
volumes can easily take the name, which is the name of the storage volume, but above volumeMounts specified time,
name and the name must be stored in the same volume, so only two were established.
c.nfs do shared storage
For convenience, the master node as a storage nfs, three nodes are performed
yum -y install nfs-utils # and then on the master boot nfs
mkdir /data/volumes
cat /etc/exports
/data/volumes 10.0.0.0/16(rw,no_root_squash)
systemctl start nfs
On node1 and node2 try to mount
mount -t nfs k8s-master:/data/volumes /mnt
cat pod-vol-nfs.yaml
apiVersion: v1
kind: Pod
metadata:
name: pod-vol-nfs
namespace: default
spec:
containers:
- name: myapp
image: ikubernetes/myapp:v2
volumeMounts:
- name: html
mountPath: /usr/share/nginx/html/
volumes:
- name: html
nfs:
path: /data/volumes
server: k8s-master
kubectl apply f pod vol nfs.yaml
At this time, regardless of the pod is built on which node, the corresponding node is not the storage of data, data on host nfs
d.pvc and pv
Pvc user need only mount the container storage volume without the need for what concerns technology used. Similar relations and relationships pvc pv pod and the Node , which consumes resources of the former, pvc size specified can apply to storage resources pv and set the access mode .
When you define a pod, we just need to explain to us how much of a storage volume on the line, pvc storage volumes must establish a direct relationship with the current namespace binding of PVC, PVC must establish a binding relationship with pv , and pv is the real one space on the storage device.
Pvc and pv is a one to one relationship, once a pv is bound with a pvc, pv then this can not be bundled with other pvc, a pvc can be accessed by multiple pod, pvc in the namespace, pv is the cluster level.
The master as a storage node, create a mount directory
cd /data/volumes && mkdir v{1,2,3,4,5}
cat /etc/exports
/data/volumes/v1 10.0.0.0/16(rw,no_root_squash)
/data/volumes/v2 10.0.0.0/16(rw,no_root_squash)
/data/volumes/v3 10.0.0.0/16(rw,no_root_squash)
exportfs -arv
showmount -e
kubectl explain pv.spec.nfs
accessModes modes are:
ReadWriteOnce: single reader, may be abbreviated as RWO;
ReadOnlyMany: multiple read-only, can be abbreviated as ROX;
ReadWriteMany: multiple read and write, can be abbreviated as RWX
# First storage device is defined as pv
cat pv-demo.yaml
apiVersion: v1
kind: PersistentVolume
metadata:
name: do not add the name space pv001 # define pv, because pv is the cluster level
labels:
name: pv001
spec:
nfs:
path: /data/volumes/v1
server: k8s-master
accessModes: ["ReadWriteMany","ReadWriteOnce"]
capacity: # allocate disk space
storage: 3Gi
---
apiVersion: v1
kind: PersistentVolume
metadata:
name: pv002
labels:
name: pv002
spec:
nfs:
path: /data/volumes/v2
server: k8s-master
accessModes: ["ReadWriteOnce"]
capacity:
storage: 5Gi
---
apiVersion: v1
kind: PersistentVolume
metadata:
name: pv003
labels:
name: pv003
spec:
nfs:
path: /data/volumes/v3
server: k8s-master
accessModes: ["ReadWriteMany","ReadWriteOnce"]
capacity:
storage: 8Gi
kubectl apply -f pv-demo.yaml
kubectl get pv
NAME CAPACITY ACCESS MODES RECLAIM POLICY STATUS
pv001 3Gi RWO,RWX Retain Available
pv002 5Gi RWO Retain Available
pv003 8Gi RWO,RWX Retain Available
Recycling Policy:
If a data stored in pv pvc inside, pvc later deleted, then how to deal with the data inside pv
reclaim_policy : That pvc deleted, but pv which data is not deleted, retained;
Recycle : i.e. pvc deleted, then put inside pv data also deleted;
the Delete : That pvc deleted, then put pv also deleted.
# Create a list of documents pvc
kubectl explain pods.spec.volumes.persistentVolumeClaim
cat pod-vol-pvc.yaml
apiVersion: v1
kind: PersistentVolumeClaim # referred pvc
metadata:
name: mypvc
namespace: default # pvc and pod in the same name space
spec:
accessModes: [ "ReadWriteMany"] # must be a subset of pv Policy
resources:
requests:
storage: 7Gi # apply for a size of at least 7G pv
---
apiVersion: v1
kind: Pod
metadata:
name: pod-vol-pvc
namespace: default
spec:
containers:
- name: myapp
image: ikubernetes/myapp:v1
volumeMounts:
- name: html storage volume using the name #
mountPath: / usr / share / nginx / html / # mount path
volumes:
- name: html
persistentVolumeClaim:
claimName: mypvc # indicates which you want to use pvc
So if the type of pod storage volume is pvc, then: pod specified pvc need to match a pv, in order to be mounted pod, after k8s 1.10, can not be manually deleted from the underlying pv.
Reference blog: http://blog.itpub.net/28916011/viewspace-2214804/