Openshift Virtualization Storage Basics

Virtualization storage is a fundamental concept in OpenShift, and understanding it is crucial for efficient deployment and management of applications.

In OpenShift, virtualization storage is provided by Container Storage Interface (CSI) drivers, which enable integration with various storage systems.

CSI drivers provide a standardized interface for interacting with storage systems, making it easier to manage and maintain storage resources.

OpenShift supports a variety of storage systems, including Red Hat Ceph Storage, Red Hat Gluster Storage, and Amazon Elastic Block Store (EBS).

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To get your VM up and running, you can use the UI or CLI. Everything can be done through the CLI or UI, and I'll show both ways here.

The UI is a great place to start, and you can create VMs and templates from the Virtualization dashboard. You can create VMs by an interactive wizard or by YAML files.

Using the wizard, you can define settings for your virtual machine, such as name, description, and template. You can also choose the source for the creation of the VM, including pxe-booting, downloading an ISO from a URL, or using a cloud image from a URL.

You can also create a VM using a YAML file, such as "fedoravm.yaml", which creates a Fedora VM from a container disk. To do this, simply run the command and your VM is being created.

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To get started, you'll need to create a project. This is where your VMs will be placed, so choose a name that makes sense, like "shared-disk-vms".

Your project name should be descriptive and easy to understand, so you can quickly identify what it's for. For example, "shared-disk-vms" clearly indicates that your VMs will be stored on a shared disk.

In this project, you'll be able to organize your VMs and manage them more efficiently. This is especially useful if you're working on a complex project that involves multiple VMs.

Make sure to choose a name that you'll remember, as you'll be using it to identify your project from now on.

You can get a VM up and running in OpenShift using the UI or CLI. The UI offers an interactive wizard for creating VMs, which can be accessed by navigating to the Virtualization dashboard.

To create a VM using the wizard, you'll need to define the settings, including the name, description, and template. You can also choose to import an existing virtual machine or create one from scratch.

One of the interesting options is to take a Container Disk as a base for a VM, which can be a great way to simplify the process.

Using the wizard, you can also configure the storage, special hardware, and Cloud-init script for the VM. Once you've defined the settings, hitting the start button will kick off the creation process.

The VM will be created with a persistent volume (PV) on the storage class you selected, and the qcow Cloud Image will be downloaded from the selected URL. A launcher pod will be created to run the VM.

You can also create a VM using a YAML file, which can be a more efficient way to create multiple VMs at once. For example, you can use a standard YAML example like "fedoravm.yaml" to create a Fedora VM from a container Disk.

To start the VM using the YAML file, you can simply run the command "oc apply -f fedoravm.yaml".

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Before diving into the setup, you'll need to create a SecurityContextConstraints (SCC) to allow the HPE CSI Driver to run with the necessary privileges.

The SCC should grant access to host ports, host network, and the ability to mount hostPath volumes. This is a crucial step, as the driver needs to be able to run in privileged mode.

The default "hpe-storage" Namespace is assumed, but you can update the ServiceAccountNamespace in the SCC if you're using a different Namespace.

Before you start, you'll need to create a SecurityContextConstraints (SCC) to allow the HPE CSI Driver to run with the necessary privileges. This includes running in privileged mode, accessing host ports and network, and mounting hostPath volumes.

The HPE CSI Driver needs to be able to run with these privileges to function properly. The default namespace for this setup is "hpe-storage", but you can update the ServiceAccountNamespace in the SCC if you want to use a different namespace.

To create the SCC, you'll need to allow the CSI driver to run in privileged mode and access host resources. This is a crucial step before deploying the HPE CSI Operator on OpenShift.

To start with, the architecture diagram I'll be referencing is based on a high-level setup.

The network will be created using OVN-Kubernetes's real-SDN capabilities. This will help facilitate inter-VM traffic.

The VMs in this setup are based on Fedora 40.

The disk is provisioned using StorageClass ocs-storagecluster-ceph-rbd-virtualization and is 10GB in size.

For this implementation, a Ceph RBD volume will suffice, as SCSI Persistent Reservation is not required.

Once the network is created, it's essential to log out as the admin user and log back in as a regular user with access to the project.

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Storage Options can be a bit overwhelming, especially when it comes to OpenShift virtualization.

You can use local storage, which is a great option for development environments or small-scale deployments.

Local storage is a good fit for environments where data is not shared across multiple nodes, such as in a single-tenant setup.

You can also use persistent volumes, which provide a more scalable and shareable storage solution.

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Persistent volumes can be provisioned dynamically or statically, depending on the needs of your application.

Another option is to use cloud storage, such as Amazon S3 or Google Cloud Storage, which can provide a highly scalable and redundant storage solution.

Cloud storage can be a good fit for large-scale deployments or applications that require high availability and durability.

To deploy NFS servers on OpenShift, you need to be aware of two key considerations for a successful deployment. Patch the hpevolumeinfoCRD to ensure a smooth setup.

Using the ext4 filesystem for NFS servers can resolve issues with stale NFS file handles on certain OpenShift versions. This can occur when the NFS server is restarted, causing problems for NFS clients.

Pre-provisioning PVCs manually is crucial if you're deploying an Operator that creates a NFS server backed PVC. This is because object references in OpenShift are not compatible with the NFS Server Provisioner, resulting in failed operations.

A shared disk is a great way to share data between multiple servers. This is especially useful in a cluster environment where multiple nodes need to access the same data.

To create a shared disk, you'll need to use a StorageClass like ocs-storagecluster-ceph-rbd-virtualization. This StorageClass has specific requirements, such as being in the same namespace as your network.

The shared disk needs to be at least 10GB in size, and it's a good idea to name it something descriptive, like "shared-disk". You'll also want to ensure it has the read-write-many (RWX) setting, which allows multiple nodes to access the disk simultaneously.

Remember, creating a shared disk requires careful planning to ensure it meets the needs of your cluster.

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To provision an NFS server successfully on OpenShift, patch the hpevolumeinfoCRD. This is essential for a smooth deployment.

You'll also need to be aware of the Limitations and Considerations for the NFS Server Provisioner in general. This will help you anticipate potential issues.

Object references in OpenShift are not compatible with the NFS Server Provisioner. This means that if a user deploys an Operator that creates a NFS server backed PVC, the operation will fail.

Pre-provision the PVC manually for the Operator instance to use, as a workaround. This ensures that the Operator can access the necessary storage.

Using the ext4 filesystem for NFS servers can help resolve issues with stale NFS file handles. This is particularly relevant on certain versions of OpenShift.

When you deploy NFS servers in a non-standard Namespace, such as "my-namespace", you need to update the "hpe-csi-nfs-scc" SCC.

To do this, you need to include the NamespaceServiceAccount in the SCC. This is necessary because the NFS server ServiceAccount is not in the default "hpe-nfs" Namespace.

This can be achieved by adding the NFS server ServiceAccount to the SCC. The example shows how to add the "my-namespace" NFS server ServiceAccount to the SCC.

You should update the SCC to include the NamespaceServiceAccount, especially when using a non-standard Namespace.

To provision a RHEL 9 PostgreSQL database, you'll need to start by creating a database VM on OpenShift Virtualization. This can be done by selecting a RHEL 9 bootable volume instead of CirrOS.

You can then register your server and start the PostgreSQL install using the dnf module.

The next step is to initialize PostgreSQL.

Finally, start and enable the postgresql service.

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To deploy the HPE CSI Operator on Red Hat OpenShift, you'll need to follow the instructions provided by Red Hat, not those found on OperatorHub.io.

The HPE CSI Operator can be installed through the interfaces provided by Red Hat.

For a step-by-step guide, check out the tutorial on YouTube, accessible through the Video Gallery, which explains how to install and use the HPE CSI Operator on Red Hat OpenShift.

Don't forget to validate your deployment to ensure everything is working as expected.

With OpenShift virtualization, you can scale your storage needs on demand, eliminating the need for manual provisioning and reducing storage costs by up to 70%.

OpenShift supports multiple storage types, including local storage, stateful sets, and persistent volumes, giving you flexibility in how you store and manage your data.

Local storage provides low-latency access to data, making it ideal for applications that require fast data access, such as databases and caching layers.

Stateful sets allow you to manage stateful applications, such as databases, without worrying about storage provisioning.

Persistent volumes provide persistent storage for stateless applications, such as web servers, and can be easily scaled up or down as needed.

By leveraging these storage options, you can create a high-performance storage environment that meets the needs of your applications.

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Testing and Verification is a crucial step in ensuring the reliability and performance of OpenShift virtualization storage. To test the shared disk, you can use a script that mounts the shared disk on both nodes and tries to read, write, and delete a single file from it.

The test script should also check system messages for any errors that may indicate a problem with the shared disk. This can help identify and troubleshoot issues before they become major problems.

Here are the specific steps involved in testing the shared disk:

CirrOS is a minimal Linux distribution designed to run on cloud platforms. It's a great choice for testing and verification because of its simplicity and small footprint.

To validate CirrOS deployment, you can use tools like Cobbler and PXE boot. Cobbler is a Linux installation server that can automate the installation process, while PXE boot allows you to boot a machine from a network location.

One way to test CirrOS deployment is to create a test environment with multiple nodes. This can be done using tools like Ansible and Terraform.

To ensure successful deployment, you can verify the integrity of the CirrOS image and the deployment process. This can be done by checking the output of the deployment process and verifying that all nodes are up and running.

A successful CirrOS deployment should result in a fully functional cloud environment. This can be tested by running various cloud-native applications and verifying that they are working as expected.

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Testing is an essential step in ensuring that your system is working as expected. It's a crucial process that helps identify and fix issues before they become major problems.

To test a shared disk, you'll need to mount it on both nodes, which involves connecting to the disk from both computers. This allows you to access the disk from either node.

Once the disk is mounted, you can try to read, write, and delete a single file from the shared disk simultaneously. This can help identify any issues with data consistency or file system integrity.

To verify that everything is working correctly, you should check the system messages for any errors. This can help you quickly identify and troubleshoot any problems that arise during testing.

Here are the key steps to test a shared disk: