Pesquisar

Este conteúdo não está disponível no idioma selecionado.

Chapter 4. Configuring a Red Hat High Availability cluster on Microsoft Azure

download PDF

To create a cluster where RHEL nodes automatically redistribute their workloads if a node failure occurs, use the Red Hat High Availability Add-On. Such high availability (HA) clusters can also be hosted on public cloud platforms, including Microsoft Azure. Creating RHEL HA clusters on Azure is similar to creating HA clusters in non-cloud environments, with certain specifics.

To configure a Red Hat HA cluster on Azure using Azure virtual machine (VM) instances as cluster nodes, see the following sections. The procedures in these sections assume that you are creating a custom image for Azure. You have a number of options for obtaining the RHEL 9 images you use for your cluster. See Red Hat Enterprise Linux Image Options on Azure for information on image options for Azure.

The following sections provide:

  • Prerequisite procedures for setting up your environment for Azure. After you set up your environment, you can create and configure Azure VM instances.
  • Procedures specific to the creation of HA clusters, which transform individual nodes into a cluster of HA nodes on Azure. These include procedures for installing the High Availability packages and agents on each cluster node, configuring fencing, and installing Azure network resource agents.

Prerequisites

4.1. The benefits of using high-availability clusters on public cloud platforms

A high-availability (HA) cluster is a set of computers (called nodes) that are linked together to run a specific workload. The purpose of HA clusters is to provide redundancy in case of a hardware or software failure. If a node in the HA cluster fails, the Pacemaker cluster resource manager distributes the workload to other nodes and no noticeable downtime occurs in the services that are running on the cluster.

You can also run HA clusters on public cloud platforms. In this case, you would use virtual machine (VM) instances in the cloud as the individual cluster nodes. Using HA clusters on a public cloud platform has the following benefits:

  • Improved availability: In case of a VM failure, the workload is quickly redistributed to other nodes, so running services are not disrupted.
  • Scalability: Additional nodes can be started when demand is high and stopped when demand is low.
  • Cost-effectiveness: With the pay-as-you-go pricing, you pay only for nodes that are running.
  • Simplified management: Some public cloud platforms offer management interfaces to make configuring HA clusters easier.

To enable HA on your Red Hat Enterprise Linux (RHEL) systems, Red Hat offers a High Availability Add-On. The High Availability Add-On provides all necessary components for creating HA clusters on RHEL systems. The components include high availability service management and cluster administration tools.

Additional resources

4.2. Creating resources in Azure

Complete the following procedure to create a region, resource group, storage account, virtual network, and availability set. You need these resources to set up a cluster on Microsoft Azure.

Procedure

  1. Authenticate your system with Azure and log in.

    $ az login
    Note

    If a browser is available in your environment, the CLI opens your browser to the Azure sign-in page.

    Example:

    [clouduser@localhost]$ az login
    
    To sign in, use a web browser to open the page https://aka.ms/devicelogin and enter the code FDMSCMETZ to authenticate.
      [
        {
          "cloudName": "AzureCloud",
          "id": "Subscription ID",
          "isDefault": true,
          "name": "MySubscriptionName",
          "state": "Enabled",
          "tenantId": "Tenant ID",
          "user": {
            "name": "clouduser@company.com",
            "type": "user"
          }
        }
      ]
  2. Create a resource group in an Azure region.

    $ az group create --name resource-group --location azure-region

    Example:

    [clouduser@localhost]$ az group create --name azrhelclirsgrp --location southcentralus
    
    {
      "id": "/subscriptions//resourceGroups/azrhelclirsgrp",
      "location": "southcentralus",
      "managedBy": null,
      "name": "azrhelclirsgrp",
      "properties": {
        "provisioningState": "Succeeded"
      },
      "tags": null
    }
  3. Create a storage account.

    $ az storage account create -l azure-region -n storage-account-name -g resource-group --sku sku_type --kind StorageV2

    Example:

    [clouduser@localhost]$ az storage account create -l southcentralus -n azrhelclistact -g azrhelclirsgrp --sku Standard_LRS --kind StorageV2
    
    {
      "accessTier": null,
      "creationTime": "2017-04-05T19:10:29.855470+00:00",
      "customDomain": null,
      "encryption": null,
      "id": "/subscriptions//resourceGroups/azrhelclirsgrp/providers/Microsoft.Storage/storageAccounts/azrhelclistact",
      "kind": "StorageV2",
      "lastGeoFailoverTime": null,
      "location": "southcentralus",
      "name": "azrhelclistact",
      "primaryEndpoints": {
        "blob": "https://azrhelclistact.blob.core.windows.net/",
        "file": "https://azrhelclistact.file.core.windows.net/",
        "queue": "https://azrhelclistact.queue.core.windows.net/",
        "table": "https://azrhelclistact.table.core.windows.net/"
    },
    "primaryLocation": "southcentralus",
    "provisioningState": "Succeeded",
    "resourceGroup": "azrhelclirsgrp",
    "secondaryEndpoints": null,
    "secondaryLocation": null,
    "sku": {
      "name": "Standard_LRS",
      "tier": "Standard"
    },
    "statusOfPrimary": "available",
    "statusOfSecondary": null,
    "tags": {},
      "type": "Microsoft.Storage/storageAccounts"
    }
  4. Get the storage account connection string.

    $ az storage account show-connection-string -n storage-account-name -g resource-group

    Example:

    [clouduser@localhost]$ az storage account show-connection-string -n azrhelclistact -g azrhelclirsgrp
    {
      "connectionString": "DefaultEndpointsProtocol=https;EndpointSuffix=core.windows.net;AccountName=azrhelclistact;AccountKey=NreGk...=="
    }
  5. Export the connection string by copying the connection string and pasting it into the following command. This string connects your system to the storage account.

    $ export AZURE_STORAGE_CONNECTION_STRING="storage-connection-string"

    Example:

    [clouduser@localhost]$ export AZURE_STORAGE_CONNECTION_STRING="DefaultEndpointsProtocol=https;EndpointSuffix=core.windows.net;AccountName=azrhelclistact;AccountKey=NreGk...=="
  6. Create the storage container.

    $ az storage container create -n container-name

    Example:

    [clouduser@localhost]$ az storage container create -n azrhelclistcont
    
    {
      "created": true
    }
  7. Create a virtual network. All cluster nodes must be in the same virtual network.

    $ az network vnet create -g resource group --name vnet-name --subnet-name subnet-name

    Example:

    [clouduser@localhost]$ az network vnet create --resource-group azrhelclirsgrp --name azrhelclivnet1 --subnet-name azrhelclisubnet1
    {
      "newVNet": {
        "addressSpace": {
          "addressPrefixes": [
          "10.0.0.0/16"
          ]
      },
      "dhcpOptions": {
        "dnsServers": []
      },
      "etag": "W/\"\"",
      "id": "/subscriptions//resourceGroups/azrhelclirsgrp/providers/Microsoft.Network/virtualNetworks/azrhelclivnet1",
      "location": "southcentralus",
      "name": "azrhelclivnet1",
      "provisioningState": "Succeeded",
      "resourceGroup": "azrhelclirsgrp",
      "resourceGuid": "0f25efee-e2a6-4abe-a4e9-817061ee1e79",
      "subnets": [
        {
          "addressPrefix": "10.0.0.0/24",
          "etag": "W/\"\"",
          "id": "/subscriptions//resourceGroups/azrhelclirsgrp/providers/Microsoft.Network/virtualNetworks/azrhelclivnet1/subnets/azrhelclisubnet1",
          "ipConfigurations": null,
          "name": "azrhelclisubnet1",
          "networkSecurityGroup": null,
          "provisioningState": "Succeeded",
          "resourceGroup": "azrhelclirsgrp",
          "resourceNavigationLinks": null,
          "routeTable": null
        }
      ],
      "tags": {},
      "type": "Microsoft.Network/virtualNetworks",
      "virtualNetworkPeerings": null
      }
    }
  8. Create an availability set. All cluster nodes must be in the same availability set.

    $ az vm availability-set create --name MyAvailabilitySet --resource-group MyResourceGroup

    Example:

    [clouduser@localhost]$ az vm availability-set create --name rhelha-avset1 --resource-group azrhelclirsgrp
    {
      "additionalProperties": {},
        "id": "/subscriptions/.../resourceGroups/azrhelclirsgrp/providers/Microsoft.Compute/availabilitySets/rhelha-avset1",
        "location": "southcentralus",
        "name": “rhelha-avset1",
        "platformFaultDomainCount": 2,
        "platformUpdateDomainCount": 5,
    
    [omitted]

4.3. Required system packages for High Availability

The procedure assumes you are creating a VM image for Azure HA that uses Red Hat Enterprise Linux. To successfully complete the procedure, the following packages must be installed.

Table 4.1. System packages
PackageRepositoryDescription

libvirt

rhel-9-for-x86_64-appstream-rpms

Open source API, daemon, and management tool for managing platform virtualization

virt-install

rhel-9-for-x86_64-appstream-rpms

A command-line utility for building VMs

libguestfs

rhel-9-for-x86_64-appstream-rpms

A library for accessing and modifying VM file systems

guestfs-tools

rhel-9-for-x86_64-appstream-rpms

System administration tools for VMs; includes the virt-customize utility

4.4. Azure VM configuration settings

Azure VMs must have the following configuration settings. Some of these settings are enabled during the initial VM creation. Other settings are set when provisioning the VM image for Azure. Keep these settings in mind as you move through the procedures. Refer to them as necessary.

Table 4.2. VM configuration settings
SettingRecommendation

ssh

ssh must be enabled to provide remote access to your Azure VMs.

dhcp

The primary virtual adapter should be configured for dhcp (IPv4 only).

Swap Space

Do not create a dedicated swap file or swap partition. You can configure swap space with the Windows Azure Linux Agent (WALinuxAgent).

NIC

Choose virtio for the primary virtual network adapter.

encryption

For custom images, use Network Bound Disk Encryption (NBDE) for full disk encryption on Azure.

4.5. Installing Hyper-V device drivers

Microsoft provides network and storage device drivers as part of their Linux Integration Services (LIS) for Hyper-V package. You may need to install Hyper-V device drivers on the VM image prior to provisioning it as an Azure virtual machine (VM). Use the lsinitrd | grep hv command to verify that the drivers are installed.

Procedure

  1. Enter the following grep command to determine if the required Hyper-V device drivers are installed.

    # lsinitrd | grep hv

    In the example below, all required drivers are installed.

    # lsinitrd | grep hv
    drwxr-xr-x   2 root     root            0 Aug 12 14:21 usr/lib/modules/3.10.0-932.el9.x86_64/kernel/drivers/hv
    -rw-r--r--   1 root     root        31272 Aug 11 08:45 usr/lib/modules/3.10.0-932.el9.x86_64/kernel/drivers/hv/hv_vmbus.ko.xz
    -rw-r--r--   1 root     root        25132 Aug 11 08:46 usr/lib/modules/3.10.0-932.el9.x86_64/kernel/drivers/net/hyperv/hv_netvsc.ko.xz
    -rw-r--r--   1 root     root         9796 Aug 11 08:45 usr/lib/modules/3.10.0-932.el9.x86_64/kernel/drivers/scsi/hv_storvsc.ko.xz

    If all the drivers are not installed, complete the remaining steps.

    Note

    An hv_vmbus driver may exist in the environment. Even if this driver is present, complete the following steps.

  2. Create a file named hv.conf in /etc/dracut.conf.d.
  3. Add the following driver parameters to the hv.conf file.

    add_drivers+=" hv_vmbus "
    add_drivers+=" hv_netvsc "
    add_drivers+=" hv_storvsc "
    add_drivers+=" nvme "
    Note

    Note the spaces before and after the quotes, for example, add_drivers+=" hv_vmbus ". This ensures that unique drivers are loaded in the event that other Hyper-V drivers already exist in the environment.

  4. Regenerate the initramfs image.

    # dracut -f -v --regenerate-all

Verification

  1. Reboot the machine.
  2. Run the lsinitrd | grep hv command to verify that the drivers are installed.

4.6. Making configuration changes required for a Microsoft Azure deployment

Before you deploy your custom base image to Azure, you must perform additional configuration changes to ensure that the virtual machine (VM) can properly operate in Azure.

Procedure

  1. Log in to the VM.
  2. Register the VM, and enable the Red Hat Enterprise Linux 9 repository.

    # subscription-manager register --auto-attach
    Installed Product Current Status:
    Product Name: Red Hat Enterprise Linux for x86_64
    Status: Subscribed
  3. Ensure that the cloud-init and hyperv-daemons packages are installed.

    # dnf install cloud-init hyperv-daemons -y
  4. Create cloud-init configuration files that are needed for integration with Azure services:

    1. To enable logging to the Hyper-V Data Exchange Service (KVP), create the /etc/cloud/cloud.cfg.d/10-azure-kvp.cfg configuration file and add the following lines to that file.

      reporting:
          logging:
              type: log
          telemetry:
              type: hyperv
    2. To add Azure as a datasource, create the /etc/cloud/cloud.cfg.d/91-azure_datasource.cfg configuration file, and add the following lines to that file.

      datasource_list: [ Azure ]
      datasource:
          Azure:
              apply_network_config: False
  5. To ensure that specific kernel modules are blocked from loading automatically, edit or create the /etc/modprobe.d/blocklist.conf file and add the following lines to that file.

    blacklist nouveau
    blacklist lbm-nouveau
    blacklist floppy
    blacklist amdgpu
    blacklist skx_edac
    blacklist intel_cstate
  6. Modify udev network device rules:

    1. Remove the following persistent network device rules if present.

      # rm -f /etc/udev/rules.d/70-persistent-net.rules
      # rm -f /etc/udev/rules.d/75-persistent-net-generator.rules
      # rm -f /etc/udev/rules.d/80-net-name-slot-rules
    2. To ensure that Accelerated Networking on Azure works as intended, create a new network device rule /etc/udev/rules.d/68-azure-sriov-nm-unmanaged.rules and add the following line to it.

      SUBSYSTEM=="net", DRIVERS=="hv_pci", ACTION=="add", ENV{NM_UNMANAGED}="1"
  7. Set the sshd service to start automatically.

    # systemctl enable sshd
    # systemctl is-enabled sshd
  8. Modify kernel boot parameters:

    1. Open the /etc/default/grub file, and ensure the GRUB_TIMEOUT line has the following value.

      GRUB_TIMEOUT=10
    2. Remove the following options from the end of the GRUB_CMDLINE_LINUX line if present.

      rhgb quiet
    3. Ensure the /etc/default/grub file contains the following lines with all the specified options.

      GRUB_CMDLINE_LINUX="loglevel=3 crashkernel=auto console=tty1 console=ttyS0 earlyprintk=ttyS0 rootdelay=300"
      GRUB_TIMEOUT_STYLE=countdown
      GRUB_TERMINAL="serial console"
      GRUB_SERIAL_COMMAND="serial --speed=115200 --unit=0 --word=8 --parity=no --stop=1"
      Note

      If you do not plan to run your workloads on HDDs, add elevator=none to the end of the GRUB_CMDLINE_LINUX line.

      This sets the I/O scheduler to none, which improves I/O performance when running workloads on SSDs.

    4. Regenerate the grub.cfg file.

      • On a BIOS-based machine:

        • In RHEL 9.2 and earlier:

          # grub2-mkconfig -o /boot/grub2/grub.cfg
        • In RHEL 9.3 and later:

          # grub2-mkconfig -o /boot/grub2/grub.cfg --update-bls-cmdline
      • On a UEFI-based machine:

        • In RHEL 9.2 and earlier:

          # grub2-mkconfig -o /boot/efi/EFI/redhat/grub.cfg
        • In RHEL 9.3 and later:

          # grub2-mkconfig -o /boot/efi/EFI/redhat/grub.cfg --update-bls-cmdline

          If your system uses a non-default location for grub.cfg, adjust the command accordingly.

  9. Configure the Windows Azure Linux Agent (WALinuxAgent):

    1. Install and enable the WALinuxAgent package.

      # dnf install WALinuxAgent -y
      # systemctl enable waagent
    2. To ensure that a swap partition is not used in provisioned VMs, edit the following lines in the /etc/waagent.conf file.

      Provisioning.DeleteRootPassword=y
      ResourceDisk.Format=n
      ResourceDisk.EnableSwap=n
  10. Prepare the VM for Azure provisioning:

    1. Unregister the VM from Red Hat Subscription Manager.

      # subscription-manager unregister
    2. Clean up the existing provisioning details.

      # waagent -force -deprovision
      Note

      This command generates warnings, which are expected because Azure handles the provisioning of VMs automatically.

    3. Clean the shell history and shut down the VM.

      # export HISTSIZE=0
      # poweroff

4.7. Creating an Azure Active Directory application

Complete the following procedure to create an Azure Active Directory (AD) application. The Azure AD application authorizes and automates access for HA operations for all nodes in the cluster.

Prerequisites

  • The Azure Command Line Interface (CLI) is installed on your system.
  • You are an Administrator or Owner for the Microsoft Azure subscription. You need this authorization to create an Azure AD application.

Procedure

  1. On any node in the HA cluster, log in to your Azure account.

    $ az login
  2. Create a json configuration file for a custom role for the Azure fence agent. Use the following configuration, but replace <subscription-id> with your subscription IDs.

    {
          "Name": "Linux Fence Agent Role",
          "description": "Allows to power-off and start virtual machines",
          "assignableScopes": [
                  "/subscriptions/<subscription-id>"
          ],
          "actions": [
                  "Microsoft.Compute/*/read",
                  "Microsoft.Compute/virtualMachines/powerOff/action",
                  "Microsoft.Compute/virtualMachines/start/action"
          ],
          "notActions": [],
          "dataActions": [],
          "notDataActions": []
    }
  3. Define the custom role for the Azure fence agent. Use the json file created in the previous step to do this.

    $ az role definition create --role-definition azure-fence-role.json
    
    {
      "assignableScopes": [
        "/subscriptions/<my-subscription-id>"
      ],
      "description": "Allows to power-off and start virtual machines",
      "id": "/subscriptions/<my-subscription-id>/providers/Microsoft.Authorization/roleDefinitions/<role-id>",
      "name": "<role-id>",
      "permissions": [
        {
          "actions": [
            "Microsoft.Compute/*/read",
            "Microsoft.Compute/virtualMachines/powerOff/action",
            "Microsoft.Compute/virtualMachines/start/action"
          ],
          "dataActions": [],
          "notActions": [],
          "notDataActions": []
        }
      ],
      "roleName": "Linux Fence Agent Role",
      "roleType": "CustomRole",
      "type": "Microsoft.Authorization/roleDefinitions"
    }
  4. In the Azure web console interface, select Virtual Machine Click Identity in the left-side menu.
  5. Select On Click Save click Yes to confirm.
  6. Click Azure role assignments Add role assignment.
  7. Select the Scope required for the role, for example Resource Group.
  8. Select the required Resource Group.
  9. Optional: Change the Subscription if necessary.
  10. Select the Linux Fence Agent Role role.
  11. Click Save.

Verification

  • Display nodes visible to Azure AD.

    # fence_azure_arm --msi -o list
    node1,
    node2,
    [...]

    If this command outputs all nodes on your cluster, the AD application has been configured successfully.

4.8. Converting the image to a fixed VHD format

All Microsoft Azure VM images must be in a fixed VHD format. The image must be aligned on a 1 MB boundary before it is converted to VHD. To convert the image from qcow2 to a fixed VHD format and align the image, see the following procedure. Once you have converted the image, you can upload it to Azure.

Procedure

  1. Convert the image from qcow2 to raw format.

    $ qemu-img convert -f qcow2 -O raw <image-name>.qcow2 <image-name>.raw
  2. Create a shell script with the following content.

    #!/bin/bash
    MB=$((1024 * 1024))
    size=$(qemu-img info -f raw --output json "$1" | gawk 'match($0, /"virtual-size": ([0-9]+),/, val) {print val[1]}')
    rounded_size=$((($size/$MB + 1) * $MB))
    if [ $(($size % $MB)) -eq  0 ]
    then
     echo "Your image is already aligned. You do not need to resize."
     exit 1
    fi
    echo "rounded size = $rounded_size"
    export rounded_size
  3. Run the script. This example uses the name align.sh.

    $ sh align.sh <image-xxx>.raw
    • If the message "Your image is already aligned. You do not need to resize." displays, proceed to the following step.
    • If a value displays, your image is not aligned.
  4. Use the following command to convert the file to a fixed VHD format.

    The sample uses qemu-img version 2.12.0.

    $ qemu-img convert -f raw -o subformat=fixed,force_size -O vpc <image-xxx>.raw <image.xxx>.vhd

    Once converted, the VHD file is ready to upload to Azure.

  5. If the raw image is not aligned, complete the following steps to align it.

    1. Resize the raw file by using the rounded value displayed when you ran the verification script.

      $ qemu-img resize -f raw <image-xxx>.raw <rounded-value>
    2. Convert the raw image file to a VHD format.

      The sample uses qemu-img version 2.12.0.

      $ qemu-img convert -f raw -o subformat=fixed,force_size -O vpc <image-xxx>.raw <image.xxx>.vhd

      Once converted, the VHD file is ready to upload to Azure.

4.9. Uploading and creating an Azure image

Complete the following steps to upload the VHD file to your container and create an Azure custom image.

Note

The exported storage connection string does not persist after a system reboot. If any of the commands in the following steps fail, export the connection string again.

Procedure

  1. Upload the VHD file to the storage container. It may take several minutes. To get a list of storage containers, enter the az storage container list command.

    $ az storage blob upload \
        --account-name <storage-account-name> --container-name <container-name> \
        --type page --file <path-to-vhd> --name <image-name>.vhd

    Example:

    [clouduser@localhost]$ az storage blob upload \
    --account-name azrhelclistact --container-name azrhelclistcont \
    --type page --file rhel-image-{ProductNumber}.vhd --name rhel-image-{ProductNumber}.vhd
    
    Percent complete: %100.0
  2. Get the URL for the uploaded VHD file to use in the following step.

    $ az storage blob url -c <container-name> -n <image-name>.vhd

    Example:

    $ az storage blob url -c azrhelclistcont -n rhel-image-9.vhd "https://azrhelclistact.blob.core.windows.net/azrhelclistcont/rhel-image-9.vhd"
  3. Create the Azure custom image.

    $ az image create -n <image-name> -g <resource-group> -l <azure-region> --source <URL> --os-type linux
    Note

    The default hypervisor generation of the VM is V1. You can optionally specify a V2 hypervisor generation by including the option --hyper-v-generation V2. Generation 2 VMs use a UEFI-based boot architecture. See Support for generation 2 VMs on Azure for information about generation 2 VMs.

    The command may return the error "Only blobs formatted as VHDs can be imported." This error may mean that the image was not aligned to the nearest 1 MB boundary before it was converted to VHD.

    Example:

    $ az image create -n rhel9 -g azrhelclirsgrp2 -l southcentralus --source https://azrhelclistact.blob.core.windows.net/azrhelclistcont/rhel-image-9.vhd --os-type linux

4.10. Installing Red Hat HA packages and agents

Complete the following steps on all nodes.

Procedure

  1. Launch an SSH terminal session and connect to the VM by using the administrator name and public IP address.

    $ ssh administrator@PublicIP

    To get the public IP address for an Azure VM, open the VM properties in the Azure Portal or enter the following Azure CLI command.

    $ az vm list -g <resource-group> -d --output table

    Example:

    [clouduser@localhost ~] $ az vm list -g azrhelclirsgrp -d --output table
    Name    ResourceGroup           PowerState      PublicIps        Location
    ------  ----------------------  --------------  -------------    --------------
    node01  azrhelclirsgrp          VM running      192.98.152.251    southcentralus
  2. Register the VM with Red Hat.

    $ sudo -i
    # subscription-manager register --auto-attach
    Note

    If the --auto-attach command fails, manually register the VM to your subscription.

  3. Disable all repositories.

    # subscription-manager repos --disable=*
  4. Enable the RHEL 9 Server HA repositories.

    # subscription-manager repos --enable=rhel-9-for-x86_64-highavailability-rpms
  5. Update all packages.

    # dnf update -y
  6. Install the Red Hat High Availability Add-On software packages, along with the Azure fencing agent from the High Availability channel.

    # dnf install pcs pacemaker fence-agents-azure-arm
  7. The user hacluster was created during the pcs and pacemaker installation in the previous step. Create a password for hacluster on all cluster nodes. Use the same password for all nodes.

    # passwd hacluster
  8. Add the high availability service to the RHEL Firewall if firewalld.service is installed.

    # firewall-cmd --permanent --add-service=high-availability
    # firewall-cmd --reload
  9. Start the pcs service and enable it to start on boot.

    # systemctl start pcsd.service
    # systemctl enable pcsd.service
    
    Created symlink from /etc/systemd/system/multi-user.target.wants/pcsd.service to /usr/lib/systemd/system/pcsd.service.

Verification

  • Ensure the pcs service is running.

    # systemctl status pcsd.service
    pcsd.service - PCS GUI and remote configuration interface
    Loaded: loaded (/usr/lib/systemd/system/pcsd.service; enabled; vendor preset: disabled)
    Active: active (running) since Fri 2018-02-23 11:00:58 EST; 1min 23s ago
    Docs: man:pcsd(8)
              man:pcs(8)
    Main PID: 46235 (pcsd)
      CGroup: /system.slice/pcsd.service
              └─46235 /usr/bin/ruby /usr/lib/pcsd/pcsd > /dev/null &

4.11. Creating a cluster

Complete the following steps to create the cluster of nodes.

Procedure

  1. On one of the nodes, enter the following command to authenticate the pcs user hacluster. In the command, specify the name of each node in the cluster.

    # pcs host auth <hostname1> <hostname2> <hostname3>

    Example:

    [root@node01 clouduser]# pcs host auth node01 node02 node03
    Username: hacluster
    Password:
    node01: Authorized
    node02: Authorized
    node03: Authorized
  2. Create the cluster.

    # pcs cluster setup <cluster_name> <hostname1> <hostname2> <hostname3>

    Example:

    [root@node01 clouduser]# pcs cluster setup new_cluster node01 node02 node03
    
    [...]
    
    Synchronizing pcsd certificates on nodes node01, node02, node03...
    node02: Success
    node03: Success
    node01: Success
    Restarting pcsd on the nodes in order to reload the certificates...
    node02: Success
    node03: Success
    node01: Success

Verification

  1. Enable the cluster.

    [root@node01 clouduser]# pcs cluster enable --all
    node02: Cluster Enabled
    node03: Cluster Enabled
    node01: Cluster Enabled
  2. Start the cluster.

    [root@node01 clouduser]# pcs cluster start --all
    node02: Starting Cluster...
    node03: Starting Cluster...
    node01: Starting Cluster...

4.12. Fencing overview

If communication with a single node in the cluster fails, then other nodes in the cluster must be able to restrict or release access to resources that the failed cluster node may have access to. This cannot be accomplished by contacting the cluster node itself as the cluster node may not be responsive. Instead, you must provide an external method, which is called fencing with a fence agent.

A node that is unresponsive may still be accessing data. The only way to be certain that your data is safe is to fence the node by using STONITH. STONITH is an acronym for "Shoot The Other Node In The Head," and it protects your data from being corrupted by rogue nodes or concurrent access. Using STONITH, you can be certain that a node is truly offline before allowing the data to be accessed from another node.

4.13. Creating a fencing device

Complete the following steps to configure fencing. Complete these commands from any node in the cluster

Prerequisites

You need to set the cluster property stonith-enabled to true.

Procedure

  1. Identify the Azure node name for each RHEL VM. You use the Azure node names to configure the fence device.

    # fence_azure_arm \
        -l <AD-Application-ID> -p <AD-Password> \
        --resourceGroup <MyResourceGroup> --tenantId <Tenant-ID> \
        --subscriptionId <Subscription-ID> -o list

    Example:

    [root@node01 clouduser]# fence_azure_arm \
    -l e04a6a49-9f00-xxxx-xxxx-a8bdda4af447 -p z/a05AwCN0IzAjVwXXXXXXXEWIoeVp0xg7QT//JE=
    --resourceGroup azrhelclirsgrp --tenantId 77ecefb6-cff0-XXXX-XXXX-757XXXX9485
    --subscriptionId XXXXXXXX-38b4-4527-XXXX-012d49dfc02c -o list
    
    node01,
    node02,
    node03,
  2. View the options for the Azure ARM STONITH agent.

    # pcs stonith describe fence_azure_arm

    Example:

    # pcs stonith describe fence_apc
    Stonith options:
    password: Authentication key
    password_script: Script to run to retrieve password
    Warning

    For fence agents that provide a method option, do not specify a value of cycle as it is not supported and can cause data corruption.

    Some fence devices can fence only a single node, while other devices can fence multiple nodes. The parameters you specify when you create a fencing device depend on what your fencing device supports and requires.

    You can use the pcmk_host_list parameter when creating a fencing device to specify all of the machines that are controlled by that fencing device.

    You can use pcmk_host_map parameter when creating a fencing device to map host names to the specifications that comprehends the fence device.

  3. Create a fence device.

    # pcs stonith create clusterfence fence_azure_arm

Verification

  1. Test the fencing agent for one of the other nodes.

    # pcs stonith fence azurenodename

    Example:

    [root@node01 clouduser]# pcs status
    Cluster name: newcluster
    Stack: corosync
    Current DC: node01 (version 1.1.18-11.el7-2b07d5c5a9) - partition with quorum
    Last updated: Fri Feb 23 11:44:35 2018
    Last change: Fri Feb 23 11:21:01 2018 by root via cibadmin on node01
    
    3 nodes configured
    1 resource configured
    
    Online: [ node01 node03 ]
    OFFLINE: [ node02 ]
    
    Full list of resources:
    
      clusterfence  (stonith:fence_azure_arm):  Started node01
    
    Daemon Status:
      corosync: active/disabled
      pacemaker: active/disabled
      pcsd: active/enabled
  2. Start the node that was fenced in the previous step.

    # pcs cluster start <hostname>
  3. Check the status to verify the node started.

    # pcs status

    Example:

    [root@node01 clouduser]# pcs status
    Cluster name: newcluster
    Stack: corosync
    Current DC: node01 (version 1.1.18-11.el7-2b07d5c5a9) - partition with quorum
    Last updated: Fri Feb 23 11:34:59 2018
    Last change: Fri Feb 23 11:21:01 2018 by root via cibadmin on node01
    
    3 nodes configured
    1 resource configured
    
    Online: [ node01 node02 node03 ]
    
    Full list of resources:
    
    clusterfence    (stonith:fence_azure_arm):  Started node01
    
    Daemon Status:
      corosync: active/disabled
      pacemaker: active/disabled
      pcsd: active/enabled

4.14. Creating an Azure internal load balancer

The Azure internal load balancer removes cluster nodes that do not answer health probe requests.

Perform the following procedure to create an Azure internal load balancer. Each step references a specific Microsoft procedure and includes the settings for customizing the load balancer for HA.

Prerequisites

Azure control panel

Procedure

  1. Create a Basic load balancer. Select Internal load balancer, the Basic SKU, and Dynamic for the type of IP address assignment.
  2. Create a back-end address pool. Associate the backend pool to the availability set created while creating Azure resources in HA. Do not set any target network IP configurations.
  3. Create a health probe. For the health probe, select TCP and enter port 61000. You can use TCP port number that does not interfere with another service. For certain HA product applications (for example, SAP HANA and SQL Server), you may need to work with Microsoft to identify the correct port to use.
  4. Create a load balancer rule. To create the load balancing rule, the default values are prepopulated. Ensure to set Floating IP (direct server return) to Enabled.

4.15. Configuring the load balancer resource agent

After you have created the health probe, you must configure the load balancer resource agent. This resource agent runs a service that answers health probe requests from the Azure load balancer and removes cluster nodes that do not answer requests.

Procedure

  1. Install the nmap-ncat resource agents on all nodes.

    # dnf install nmap-ncat resource-agents-cloud

    Perform the following steps on a single node.

  2. Create the pcs resources and group. Use your load balancer FrontendIP for the IPaddr2 address.

    # pcs resource create resource-name IPaddr2 ip="10.0.0.7" --group cluster-resources-group
  3. Configure the load balancer resource agent.

    # pcs resource create resource-loadbalancer-name azure-lb port=port-number --group cluster-resources-group

Verification

  • Run pcs status to see the results.

    [root@node01 clouduser]# pcs status

    Example output:

    Cluster name: clusterfence01
    Stack: corosync
    Current DC: node02 (version 1.1.16-12.el7_4.7-94ff4df) - partition with quorum
    Last updated: Tue Jan 30 12:42:35 2018
    Last change: Tue Jan 30 12:26:42 2018 by root via cibadmin on node01
    
    3 nodes configured
    3 resources configured
    
    Online: [ node01 node02 node03 ]
    
    Full list of resources:
    
    clusterfence (stonith:fence_azure_arm):      Started node01
    Resource Group: g_azure
        vip_azure  (ocf::heartbeat:IPaddr2):       Started node02
        lb_azure   (ocf::heartbeat:azure-lb):      Started node02
    
    Daemon Status:
      corosync: active/disabled
      pacemaker: active/disabled
      pcsd: active/enabled

4.16. Configuring shared block storage

To configure shared block storage for a Red Hat High Availability cluster with Microsoft Azure Shared Disks, use the following procedure. Note that this procedure is optional, and the steps below assume three Azure VMs (a three-node cluster) with a 1 TB shared disk.

Note

This is a stand-alone sample procedure for configuring block storage. The procedure assumes that you have not yet created your cluster.

Prerequisites

Procedure

  1. Create a shared block volume by using the Azure command az disk create.

    $ az disk create -g <resource_group> -n <shared_block_volume_name> --size-gb <disk_size> --max-shares <number_vms> -l <location>

    For example, the following command creates a shared block volume named shared-block-volume.vhd in the resource group sharedblock within the Azure Availability Zone westcentralus.

    $ az disk create -g sharedblock-rg -n shared-block-volume.vhd --size-gb 1024 --max-shares 3 -l westcentralus
    
    {
      "creationData": {
        "createOption": "Empty",
        "galleryImageReference": null,
        "imageReference": null,
        "sourceResourceId": null,
        "sourceUniqueId": null,
        "sourceUri": null,
        "storageAccountId": null,
        "uploadSizeBytes": null
      },
      "diskAccessId": null,
      "diskIopsReadOnly": null,
      "diskIopsReadWrite": 5000,
      "diskMbpsReadOnly": null,
      "diskMbpsReadWrite": 200,
      "diskSizeBytes": 1099511627776,
      "diskSizeGb": 1024,
      "diskState": "Unattached",
      "encryption": {
        "diskEncryptionSetId": null,
        "type": "EncryptionAtRestWithPlatformKey"
      },
      "encryptionSettingsCollection": null,
      "hyperVgeneration": "V1",
      "id": "/subscriptions/12345678910-12345678910/resourceGroups/sharedblock-rg/providers/Microsoft.Compute/disks/shared-block-volume.vhd",
      "location": "westcentralus",
      "managedBy": null,
      "managedByExtended": null,
      "maxShares": 3,
      "name": "shared-block-volume.vhd",
      "networkAccessPolicy": "AllowAll",
      "osType": null,
      "provisioningState": "Succeeded",
      "resourceGroup": "sharedblock-rg",
      "shareInfo": null,
      "sku": {
        "name": "Premium_LRS",
        "tier": "Premium"
      },
      "tags": {},
      "timeCreated": "2020-08-27T15:36:56.263382+00:00",
      "type": "Microsoft.Compute/disks",
      "uniqueId": "cd8b0a25-6fbe-4779-9312-8d9cbb89b6f2",
      "zones": null
    }
  2. Verify that you have created the shared block volume by using the Azure command az disk show.

    $ az disk show -g <resource_group> -n <shared_block_volume_name>

    For example, the following command shows details for the shared block volume shared-block-volume.vhd within the resource group sharedblock-rg.

    $ az disk show -g sharedblock-rg -n shared-block-volume.vhd
    
    {
      "creationData": {
        "createOption": "Empty",
        "galleryImageReference": null,
        "imageReference": null,
        "sourceResourceId": null,
        "sourceUniqueId": null,
        "sourceUri": null,
        "storageAccountId": null,
        "uploadSizeBytes": null
      },
      "diskAccessId": null,
      "diskIopsReadOnly": null,
      "diskIopsReadWrite": 5000,
      "diskMbpsReadOnly": null,
      "diskMbpsReadWrite": 200,
      "diskSizeBytes": 1099511627776,
      "diskSizeGb": 1024,
      "diskState": "Unattached",
      "encryption": {
        "diskEncryptionSetId": null,
        "type": "EncryptionAtRestWithPlatformKey"
      },
      "encryptionSettingsCollection": null,
      "hyperVgeneration": "V1",
      "id": "/subscriptions/12345678910-12345678910/resourceGroups/sharedblock-rg/providers/Microsoft.Compute/disks/shared-block-volume.vhd",
      "location": "westcentralus",
      "managedBy": null,
      "managedByExtended": null,
      "maxShares": 3,
      "name": "shared-block-volume.vhd",
      "networkAccessPolicy": "AllowAll",
      "osType": null,
      "provisioningState": "Succeeded",
      "resourceGroup": "sharedblock-rg",
      "shareInfo": null,
      "sku": {
        "name": "Premium_LRS",
        "tier": "Premium"
      },
      "tags": {},
      "timeCreated": "2020-08-27T15:36:56.263382+00:00",
      "type": "Microsoft.Compute/disks",
      "uniqueId": "cd8b0a25-6fbe-4779-9312-8d9cbb89b6f2",
      "zones": null
    }
  3. Create three network interfaces by using the Azure command az network nic create. Run the following command three times by using a different <nic_name> for each.

    $ az network nic create \
        -g <resource_group> -n <nic_name> --subnet <subnet_name> \
        --vnet-name <virtual_network> --location <location> \
        --network-security-group <network_security_group> --private-ip-address-version IPv4

    For example, the following command creates a network interface with the name shareblock-nodea-vm-nic-protected.

    $ az network nic create \
        -g sharedblock-rg -n sharedblock-nodea-vm-nic-protected --subnet sharedblock-subnet-protected \
        --vnet-name sharedblock-vn --location westcentralus \
        --network-security-group sharedblock-nsg --private-ip-address-version IPv4
  4. Create three VMs and attach the shared block volume by using the Azure command az vm create. Option values are the same for each VM except that each VM has its own <vm_name>, <new_vm_disk_name>, and <nic_name>.

    $ az vm create \
        -n <vm_name> -g <resource_group> --attach-data-disks <shared_block_volume_name> \
        --data-disk-caching None --os-disk-caching ReadWrite --os-disk-name <new-vm-disk-name> \
        --os-disk-size-gb <disk_size> --location <location> --size <virtual_machine_size> \
        --image <image_name> --admin-username <vm_username> --authentication-type ssh \
        --ssh-key-values <ssh_key> --nics <nic_name> --availability-set <availability_set> --ppg <proximity_placement_group>

    For example, the following command creates a VM named sharedblock-nodea-vm.

    $ az vm create \
    -n sharedblock-nodea-vm -g sharedblock-rg --attach-data-disks shared-block-volume.vhd \
    --data-disk-caching None --os-disk-caching ReadWrite --os-disk-name sharedblock-nodea-vm.vhd \
    --os-disk-size-gb 64 --location westcentralus --size Standard_D2s_v3 \
    --image /subscriptions/12345678910-12345678910/resourceGroups/sample-azureimagesgroupwestcentralus/providers/Microsoft.Compute/images/sample-azure-rhel-9.3.0-20200713.n.0.x86_64 --admin-username sharedblock-user --authentication-type ssh \
    --ssh-key-values @sharedblock-key.pub --nics sharedblock-nodea-vm-nic-protected --availability-set sharedblock-as --ppg sharedblock-ppg
    
    {
      "fqdns": "",
      "id": "/subscriptions/12345678910-12345678910/resourceGroups/sharedblock-rg/providers/Microsoft.Compute/virtualMachines/sharedblock-nodea-vm",
      "location": "westcentralus",
      "macAddress": "00-22-48-5D-EE-FB",
      "powerState": "VM running",
      "privateIpAddress": "198.51.100.3",
      "publicIpAddress": "",
      "resourceGroup": "sharedblock-rg",
      "zones": ""
    }

Verification

  1. For each VM in your cluster, verify that the block device is available by using the ssh command with your VM’s IP address.

    # ssh <ip_address> "hostname ; lsblk -d | grep ' 1T '"

    For example, the following command lists details including the host name and block device for the VM IP 198.51.100.3.

    # ssh 198.51.100.3 "hostname ; lsblk -d | grep ' 1T '"
    
    nodea
    sdb    8:16   0    1T  0 disk
  2. Use the ssh command to verify that each VM in your cluster uses the same shared disk.

    # ssh <ip_address> "hostname ; lsblk -d | grep ' 1T ' | awk '{print \$1}' | xargs -i udevadm info --query=all --name=/dev/{} | grep '^E: ID_SERIAL='"

    For example, the following command lists details including the host name and shared disk volume ID for the instance IP address 198.51.100.3.

    # ssh 198.51.100.3 "hostname ; lsblk -d | grep ' 1T ' | awk '{print \$1}' | xargs -i udevadm info --query=all --name=/dev/{} | grep '^E: ID_SERIAL='"
    
    nodea
    E: ID_SERIAL=3600224808dd8eb102f6ffc5822c41d89

After you have verified that the shared disk is attached to each VM, you can configure resilient storage for the cluster.

4.17. Additional resources

Red Hat logoGithubRedditYoutubeTwitter

Aprender

Experimente, compre e venda

Comunidades

Sobre a documentação da Red Hat

Ajudamos os usuários da Red Hat a inovar e atingir seus objetivos com nossos produtos e serviços com conteúdo em que podem confiar.

Tornando o open source mais inclusivo

A Red Hat está comprometida em substituir a linguagem problemática em nosso código, documentação e propriedades da web. Para mais detalhes veja oBlog da Red Hat.

Sobre a Red Hat

Fornecemos soluções robustas que facilitam o trabalho das empresas em plataformas e ambientes, desde o data center principal até a borda da rede.

© 2024 Red Hat, Inc.