第1章 Using dynamic storage with the LVMS plugin
Using dynamic provisioning allows you to create storage volumes on-demand, eliminating the need for pre-provisioned storage.
MicroShift enables dynamic storage provisioning that is ready for immediate use with the logical volume manager storage (LVMS) Container Storage Interface (CSI) provider. The LVMS plugin is the Red Hat downstream version of TopoLVM, a CSI plugin for managing logical volume management (LVM) logical volumes (LVs) for Kubernetes.
LVMS provisions new LVM logical volumes for container workloads with appropriately configured persistent volume claims (PVCs). Each PVC references a storage class that represents an LVM Volume Group (VG) on the host node. LVs are only provisioned for scheduled pods.
1.1. LVMS system requirements
Using LVMS in MicroShift requires the following system specifications.
1.1.1. Volume group name
If you did not configure LVMS in an lvmd.yaml file placed in the /etc/microshift/ directory, MicroShift attempts to assign a default volume group (VG) dynamically by running the vgs command.
- MicroShift assigns a default VG when only one VG is found.
-
If more than one VG is present, the VG named
microshiftis assigned as the default. -
If a VG named
microshiftdoes not exist, LVMS is not deployed.
If there are no volume groups on the MicroShift host, LVMS is disabled.
If you want to use a specific VG, LVMS must be configured to select that VG. You can change the default name of the VG in the configuration file. For details, read the "Configuring the LVMS" section of this document.
You can change the default name of the VG in the configuration file. For details, read the "Configuring the LVMS" section of this document.
After MicroShift starts, you can update the lvmd.yaml to include or remove VGs. To implement changes, you must restart MicroShift. If the lvmd.yaml is deleted, MicroShift attempts to find a default VG again.
1.1.2. Volume size increments
The LVMS provisions storage in increments of 1 gigabyte (GB). Storage requests are rounded up to the nearest GB. When the capacity of a VG is less than 1 GB, the PersistentVolumeClaim registers a ProvisioningFailed event, for example:
Example output
Warning ProvisioningFailed 3s (x2 over 5s) topolvm.cybozu.com_topolvm-controller-858c78d96c-xttzp_0fa83aef-2070-4ae2-bcb9-163f818dcd9f failed to provision volume with
StorageClass "topolvm-provisioner": rpc error: code = ResourceExhausted desc = no enough space left on VG: free=(BYTES_INT), requested=(BYTES_INT)
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