This section covers OpenEBS persistent storage solution using AWS instance store disks for applications running on Kubernetes clusters. Instance store disks provide high performance, but they are not guaranteed to be present in the node all the time which of course means that when the node is rescheduled you can lose the data they are storing.
Instance store is ideal for temporary storage of information that changes frequently, such as buffers, caches, scratch data, and other temporary content or for data that is replicated across a fleet of instances, such as a load-balanced pool of web servers.
Instance Store volume's drawback is that the data in an instance store persists only during the lifetime of its associated instance. The data in the instance store may be lost due to the following:
- Underlying disk drive fails
- Instance stops
- Instance terminates
OpenEBS with AWS Instance Store
Some instance types use NVMe or SATA-based solid state drives (SSD) to deliver high random I/O performance. This is a good option when you need storage with very low latency and do not need the data to persist when the instance terminates. You can also take advantage of fault-tolerant architectures. OpenEBS is an option for high availability of data combined with the advantages of using physical disks.
How is replication done with OpenEBS?
OpenEBS will have minimum 3 replicas to run OpenEBS cluster with high availability and if a node fails, OpenEBS will manage the data to be replicated to a new disk which will come up as part of ASG. In the meantime, your workload is accessing the live data from one the replicas.
- AWS account with full access to EC2, S3, and VPC
- Ubuntu 16.04
- KOPS tool installed
- AWS CLI installed for AWS account access
- SSH key generated to access EC2 instances
Installing OpenEBS Cluster in AWS
Use local ubuntu 16.04 machine from where you can login to AWS with appropriate user credentials and creating a cluster from it.
Perform following operations from AWS management console
- Create VPC and Internet gateway.
- Associate this VPC with the Internet Gateway.
Perform the following procedure from your local ubuntu machine
Download AWSCLI utility in your local machine.
Configure with your AWS account by executing the following command.
Note: You have to specify your AWS Access Key, Secret Access Key, Default region name, and Default output format for keeping the configuration details.
Create a S3 bucket to store your cluster configuration details as follows.
aws s3 mb s3://<bucket_name>
Export the s3 bucket details using the following command.
Create the cluster across different zones using following command.
kops create cluster --name=<cluster_name>.k8s.local --vpc=<vpc_id> --zones==<zone1_name>,<zone2_name>,<zone3_name>
This will create a cluster in the mentioned zone in your region provided as part of AWS configuration.
The above step will give a set of commands which can be used for customizing your cluster configuration such as Cluster name change, Instance group for Nodes, and master etc. Following is an example output.
Cluster configuration has been created.
- list clusters with: kops get cluster
- edit this cluster with : kops edit cluster ranjith.k8s.local
- edit your node instance group: kops edit ig --name=ranjith.k8s.local nodes
- edit your master instance group: kops edit ig --name=ranjith.k8s.local master-us-west-2a
Finally, configure your cluster with: kops update cluster name.k8s.local --yes
Change your instance image type and number of machines by executing corresponding commands. The exact command needed for your cluster will be shown at the end of the previous step. Following is an example.
Change your node configuration by executing as follows.
kops edit ig --name=<cluster_name>.k8s.local nodes
Change your master instance type and number of machines by executing as follows.
kops edit ig --name=<cluster_name>.k8s.local master-<zone_name>
Note: We used c3.xlarge as instance type for both Master and Nodes. Number nodes used is 3.
Once the customization is done, you can update the changes as follows.
kops update cluster <cluster_name>.k8s.local --yes
The above step will deploy a 3 Node OpenEBS cluster in AWS. You can check the instance creation status by going to EC2 instance page and choosing the corresponding region.
From EC2 instance page, you will get each instance type Public IP.
Go to Launch Configuration section in the EC2 page and take a copy of Launch configuration for nodes. Select the configuration for Node group and click on Actions pane.
Perform changes in the Configure Details section as follows.
Change the new configuration name if required.
Edit Advanced Details section and add the following entry at the end of User data section.
set -x date apt-get install open-iscsi grep "@reboot root sleep 120;service open-iscsi restart" /etc/crontab || sudo sh -c 'echo "@reboot root sleep 120;service open-iscsi restart" >> /etc/crontab' systemctl enable open-iscsi sh -c 'echo "/dev/xvdd /mnt/openebs_xvdd auto defaults,nofail,comment=cloudconfig 0 2" >> /etc/fstab' reboot set -x umount /mnt/openebs/xvdd mount /dev/xvdd /mnt/openebs_xvdd
Click Skip to review and proceed with Create launch configuration.
Go to Auto Scale Group section in the EC2 page. Select the configuration for Node group and click on Actions pane to edit Launch Configuration. Change the existing one with new Launch Configuration and save the new configuration.
SSH to each node using its public key as follows.
ssh -i ~/.ssh/id_rsa admin@<public_ip>
SSH to all the Nodes where OpenEBS will be installed and perform the following commands to install iSCSI packages ,unmount local ssd disks and auto mounting of local disks to the given mountpoint during reboot.
sudo apt-get update sudo apt-get install open-iscsi sudo service open-iscsi restart sudo cat /etc/iscsi/initiatorname.iscsi sudo service open-iscsi status sudo sudo sh -c 'echo "/dev/xvdd /mnt/openebs_xvdd auto defaults,nofail,comment=cloudconfig 0 2" >> /etc/fstab' grep "@reboot root sleep 120;service open-iscsi restart" /etc/crontab || sudo sh -c 'echo "@reboot root sleep 120;service open-iscsi restart" >> /etc/crontab' sudo reboot
SSH to Master Node and perform the following commands to clone OpenEBS yaml file and deploy.
kubectl apply -f https://openebs.github.io/charts/openebs-operator-0.7.0.yaml
Create a storage pool on an external disk which is mounted on the nodes. To create a storage pool, create a file called “openebs-config.yaml” file in your master node and add the below example YAML with changing the appropriate mounted disk path.
For example,If your external disk is mounted as "/mnt/openebs_xvdd" in your nodes, change the path as below.
path: “ openebs_xvdd”
Example yaml file:
apiVersion: openebs.io/v1alpha1 kind: StoragePool metadata: name: default type: hostdir spec: path: "/mnt/openebs_xvdd"
Apply the modified openebs-config.yaml file by using the following command.
``` kubectl apply -f openebs-config.yaml ``` This will create a storage pool called “default” on selected disk.
Now storage pool is created on the Nodes as per your requirement. You can get the storage pool details by running the following command.
Now you are configured OpenEBS Jiva storage engine which will create OpenEBS Jiva volume on the storage pool created on local SSD disk.
Deploy your application yaml which will be created on the local disk. Get the percona deploymnet YAML file using following command
Edit the downloaded “percona-openebs-deployment.yaml” and do the following changes.
Under "PersistentVolumeClaim" section,change the “storageClassName” to “openebs-jiva-default” from ”openebs-standard”.
Save the modified changes and apply the YAML as follows.
kubectl apply -f percona-openebs-deployment.yaml
This will create a PVC and PV in mentioned size. You can get the PVC status by running the following command.
kubectl get pvc
Following is an example output.
NAME STATUS VOLUME CAPACITY ACCESS MODES STORAGECLASS AGE demo-vol1-claim Bound default-demo-vol1-claim-2300073071 G RWO openebs-jiva-default 1m
Get the status of PV using the following command.
kubectl get pv
Output of the above command will be similar to the following.
NAME CAPACITY ACCESS MODES RECLAIM POLICY STATUS CLAIM STORAGECLASS REASON AGE default-demo-vol1-claim-1171753629 5G RWO Delete Bound default/demo-vol1-claim openebs-jiva-default 17s
Now, your Percona application pod will be running along with three Jiva volume replica and One Jiva Controller pod. You can get the running pod status by running the following command:
kubectl get pods -o wide
Output similar to the following is displayed.
NAME READY STATUS RESTARTS AGE IP NODE default-demo-vol1-claim-1171753629-ctrl-5fb888f54-jzxsw 2/2 Running 0 1m 100.96.2.8 ip-10-0-55-5.us-west-2.compute.internal default-demo-vol1-claim-1171753629-rep-78767568b6-gcqtd 1/1 Running 0 1m 100.96.2.9 ip-10-0-55-5.us-west-2.compute.internal default-demo-vol1-claim-1171753629-rep-78767568b6-lw4dl 1/1 Running 0 1m 100.96.1.7 ip-10-0-91-227.us-west-2.compute.internal default-demo-vol1-claim-1171753629-rep-78767568b6-zlfl9 1/1 Running 0 1m 100.96.3.7 ip-10-0-100-78.us-west-2.compute.internal percona-7f6bff67f6-dnrbr 1/1 Running 0 1m 100.96.1.8 ip-10-0-91-227.us-west-2.compute.internal