Chapter 9. Deploying on OpenStack with rootVolume and etcd on local disk As a day 2 operation, you can resolve and prevent performance issues of your Red Hat OpenStack Platform (RHOSP) installation by moving etcd from a root volume (provided by OpenStack Cinder) to a dedicated ephemeral local disk. 9.1. Deploying RHOSP on local disk If you have an existing RHOSP cloud, you can move etcd from that cloud to a dedicated ephemeral local disk. Prerequisites You have an OpenStack cloud with a working Cinder. Your OpenStack cloud has at least 75 GB of available storage to accommodate 3 root volumes for the OpenShift control plane. The OpenStack cloud is deployed with Nova ephemeral storage that uses a local storage backend and not rbd . Procedure Create a Nova flavor for the control plane with at least 10 GB of ephemeral disk by running the following command, replacing the values for --ram , --disk , and <flavor_name> based on your environment: USD openstack flavor create --<ram 16384> --<disk 0> --ephemeral 10 --vcpus 4 <flavor_name> Deploy a cluster with root volumes for the control plane; for example: Example YAML file # ... controlPlane: name: master platform: openstack: type: USD{CONTROL_PLANE_FLAVOR} rootVolume: size: 25 types: - USD{CINDER_TYPE} replicas: 3 # ... Deploy the cluster you created by running the following command: USD openshift-install create cluster --dir <installation_directory> 1 1 For <installation_directory> , specify the location of the customized ./install-config.yaml file that you previously created. Verify that the cluster you deployed is healthy before proceeding to the step by running the following command: USD oc wait clusteroperators --all --for=condition=Progressing=false 1 1 Ensures that the cluster operators are finished progressing and that the cluster is not deploying or updating. Create a file named 98-var-lib-etcd.yaml by using the following YAML file: apiVersion: machineconfiguration.openshift.io/v1 kind: MachineConfig metadata: labels: machineconfiguration.openshift.io/role: master name: 98-var-lib-etcd spec: config: ignition: version: 3.4.0 systemd: units: - contents: | [Unit] Description=Mount local-etcd to /var/lib/etcd [Mount] What=/dev/disk/by-label/local-etcd 1 Where=/var/lib/etcd Type=xfs Options=defaults,prjquota [Install] WantedBy=local-fs.target enabled: true name: var-lib-etcd.mount - contents: | [Unit] Description=Create local-etcd filesystem DefaultDependencies=no After=local-fs-pre.target ConditionPathIsSymbolicLink=!/dev/disk/by-label/local-etcd 2 [Service] Type=oneshot RemainAfterExit=yes ExecStart=/bin/bash -c "[ -L /dev/disk/by-label/ephemeral0 ] || ( >&2 echo Ephemeral disk does not exist; /usr/bin/false )" ExecStart=/usr/sbin/mkfs.xfs -f -L local-etcd /dev/disk/by-label/ephemeral0 3 [Install] RequiredBy=dev-disk-by\x2dlabel-local\x2detcd.device enabled: true name: create-local-etcd.service - contents: | [Unit] Description=Migrate existing data to local etcd After=var-lib-etcd.mount Before=crio.service 4 Requisite=var-lib-etcd.mount ConditionPathExists=!/var/lib/etcd/member ConditionPathIsDirectory=/sysroot/ostree/deploy/rhcos/var/lib/etcd/member 5 [Service] Type=oneshot RemainAfterExit=yes ExecStart=/bin/bash -c "if [ -d /var/lib/etcd/member.migrate ]; then rm -rf /var/lib/etcd/member.migrate; fi" 6 ExecStart=/usr/bin/cp -aZ /sysroot/ostree/deploy/rhcos/var/lib/etcd/member/ /var/lib/etcd/member.migrate ExecStart=/usr/bin/mv /var/lib/etcd/member.migrate /var/lib/etcd/member 7 [Install] RequiredBy=var-lib-etcd.mount enabled: true name: migrate-to-local-etcd.service - contents: | [Unit] Description=Relabel /var/lib/etcd After=migrate-to-local-etcd.service Before=crio.service Requisite=var-lib-etcd.mount [Service] Type=oneshot RemainAfterExit=yes ExecCondition=/bin/bash -c "[ -n \"USD(restorecon -nv /var/lib/etcd)\" ]" 8 ExecStart=/usr/sbin/restorecon -R /var/lib/etcd [Install] RequiredBy=var-lib-etcd.mount enabled: true name: relabel-var-lib-etcd.service 1 The etcd database must be mounted by the device, not a label, to ensure that systemd generates the device dependency used in this config to trigger filesystem creation. 2 Do not run if the file system dev/disk/by-label/local-etcd already exists. 3 Fails with an alert message if /dev/disk/by-label/ephemeral0 does not exist. 4 Migrates existing data to local etcd database. This config does so after /var/lib/etcd is mounted, but before CRI-O starts so etcd is not running yet. 5 Requires that etcd is mounted and does not contain a member directory, but the ostree does. 6 Cleans up any migration state. 7 Copies and moves in separate steps to ensure atomic creation of a complete member directory. 8 Performs a quick check of the mount point directory before performing a full recursive relabel. If restorecon in the file path /var/lib/etcd cannot rename the directory, the recursive rename is not performed. Warning After you apply the 98-var-lib-etcd.yaml file to the system, do not remove it. Removing this file will break etcd members and lead to system instability. If a rollback is necessary, modify the ControlPlaneMachineSet object to use a flavor that does not include ephemeral disks. This change regenerates the control plane nodes without using ephemeral disks for the etcd partition, which avoids issues related to the 98-var-lib-etcd.yaml file. It is safe to remove the 98-var-lib-etcd.yaml file only after the update to the ControlPlaneMachineSet object is complete and no control plane nodes are using ephemeral disks. Create the new MachineConfig object by running the following command: USD oc create -f 98-var-lib-etcd.yaml Note Moving the etcd database onto the local disk of each control plane machine takes time. Verify that the etcd databases has been transferred to the local disk of each control plane by running the following commands: Verify that the cluster is still updating by running the following command: USD oc wait --timeout=45m --for=condition=Updating=false machineconfigpool/master Verify that the cluster is ready by running the following command: USD oc wait node --selector='node-role.kubernetes.io/master' --for condition=Ready --timeout=30s Verify that the cluster Operators are running in the cluster by running the following command: USD oc wait clusteroperators --timeout=30m --all --for=condition=Progressing=false 9.2. Additional resources Recommended etcd practices Overview of backup and restore options

Commands:
openstack flavor create --<ram 16384> --<disk 0> --ephemeral 10 --vcpus 4 <flavor_name>
controlPlane: name: master platform: openstack: type: USD{CONTROL_PLANE_FLAVOR} rootVolume: size: 25 types: - USD{CINDER_TYPE} replicas: 3
openshift-install create cluster --dir <installation_directory> 1
oc wait clusteroperators --all --for=condition=Progressing=false 1
apiVersion: machineconfiguration.openshift.io/v1 kind: MachineConfig metadata: labels: machineconfiguration.openshift.io/role: master name: 98-var-lib-etcd spec: config: ignition: version: 3.4.0 systemd: units: - contents: | [Unit] Description=Mount local-etcd to /var/lib/etcd [Mount] What=/dev/disk/by-label/local-etcd 1 Where=/var/lib/etcd Type=xfs Options=defaults,prjquota [Install] WantedBy=local-fs.target enabled: true name: var-lib-etcd.mount - contents: | [Unit] Description=Create local-etcd filesystem DefaultDependencies=no After=local-fs-pre.target ConditionPathIsSymbolicLink=!/dev/disk/by-label/local-etcd 2 [Service] Type=oneshot RemainAfterExit=yes ExecStart=/bin/bash -c "[ -L /dev/disk/by-label/ephemeral0 ] || ( >&2 echo Ephemeral disk does not exist; /usr/bin/false )" ExecStart=/usr/sbin/mkfs.xfs -f -L local-etcd /dev/disk/by-label/ephemeral0 3 [Install] RequiredBy=dev-disk-by\x2dlabel-local\x2detcd.device enabled: true name: create-local-etcd.service - contents: | [Unit] Description=Migrate existing data to local etcd After=var-lib-etcd.mount Before=crio.service 4 Requisite=var-lib-etcd.mount ConditionPathExists=!/var/lib/etcd/member ConditionPathIsDirectory=/sysroot/ostree/deploy/rhcos/var/lib/etcd/member 5 [Service] Type=oneshot RemainAfterExit=yes ExecStart=/bin/bash -c "if [ -d /var/lib/etcd/member.migrate ]; then rm -rf /var/lib/etcd/member.migrate; fi" 6 ExecStart=/usr/bin/cp -aZ /sysroot/ostree/deploy/rhcos/var/lib/etcd/member/ /var/lib/etcd/member.migrate ExecStart=/usr/bin/mv /var/lib/etcd/member.migrate /var/lib/etcd/member 7 [Install] RequiredBy=var-lib-etcd.mount enabled: true name: migrate-to-local-etcd.service - contents: | [Unit] Description=Relabel /var/lib/etcd After=migrate-to-local-etcd.service Before=crio.service Requisite=var-lib-etcd.mount [Service] Type=oneshot RemainAfterExit=yes ExecCondition=/bin/bash -c "[ -n \"USD(restorecon -nv /var/lib/etcd)\" ]" 8 ExecStart=/usr/sbin/restorecon -R /var/lib/etcd [Install] RequiredBy=var-lib-etcd.mount enabled: true name: relabel-var-lib-etcd.service
oc create -f 98-var-lib-etcd.yaml
oc wait --timeout=45m --for=condition=Updating=false machineconfigpool/master
oc wait node --selector='node-role.kubernetes.io/master' --for condition=Ready --timeout=30s
oc wait clusteroperators --timeout=30m --all --for=condition=Progressing=false