Thin Provisioning

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• Overview
• Creating a Thin-Provisioned Volume for Replicated PV Mayastor
• Creating a Thin-Provisioned Volume for Local PV LVM
• Creating a Thin-Provisioned Volume for Local PV ZFS
• Benefits of Thin Provisioning

Overview

Thin Provisioning is a storage optimization strategy that enables the allocation of storage resources on-demand, rather than pre-allocating the entire storage upfront. This approach is particularly beneficial for maximizing storage utilization and delaying hardware expansion costs.

You can create virtual volumes that appear larger than the available physical capacity by using thin provisioning techniques. However, it is important to monitor and manage these volumes to avoid performance degradation or storage depletion.

Creating a Thin-Provisioned Volume for Replicated PV Mayastor

To enable thin provisioning, set thin: true under the parameters specification in the StorageClass definition. Refer to the StorageClass Parameters Documentation for more information.

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: mayastor-1
parameters:
  protocol: nvmf
  repl: "1"  
  thin: "true"
provisioner: io.openebs.csi-mayastor
allowVolumeExpansion: true

Creating a Thin-Provisioned Volume for Local PV LVM

To enable thin provisioning, set the thinProvision parameter to "yes" in the StorageClass definition. If this parameter is omitted, the volume is created as thick-provisioned by default.

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
 name: lvm-sc
allowVolumeExpansion: true
provisioner: local.csi.openebs.io
parameters:
  volgroup: "lvmvg"
  thinProvision: "yes"

Ensure the dm_thin_pool kernel module is loaded on all nodes before creating thin-provisioned volumes.

Verifying Kernel Module Availability

Run the following command on all nodes to verify that the required kernel module is loaded:

lsmod | grep dm_thin_pool

If the module is not loaded, load it using:

modprobe dm_thin_pool

Extending the Thin Pool Size

Thin pools are implemented as logical volumes. You can extend their size using the lvextend command. Note that reducing the size of a thin pool is not supported.

lvextend -L +15G lvmvg/thin_pool

Extending logical volume thin_pool to 30.00 GiB
Logical volume mythinpool successfully resized

Configuring Auto-Extension for Thin Pools

By default, auto-extension of thin pools is not enabled. This allows you to retain control over pool growth, especially in environments where limits must be enforced manually.

To enable automatic extension monitoring, the thin pool must be explicitly monitored using lvchange.

1. Check Monitoring Status.

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   Verify if Thin Pool Monitoring is Enabled

   lvs -o+seg_monitor

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   Sample Output

   LV             VG    Attr       LSize Pool           Origin Data%  Meta%  Move Log Cpy%Sync Convert Monitor
   lvmvg_thinpool lvmvg twi-aotz-- 2.07g                       0.00   11.52                            not monitored

   If the Monitor column indicates not monitored, proceed to enable monitoring.

2. Enable Monitoring.

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   Enable Monitoring for Thin Pool

   lvchange --monitor y lvmvg/lvmvg_thinpool

   Verify that the monitoring is enabled:

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   Confirm Monitoring Status

   lvs -o+seg_monitor

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   Sample Output

   LV             VG    Attr       LSize Pool           Origin Data%  Meta%  Move Log Cpy%Sync Convert Monitor
   lvmvg_thinpool lvmvg twi-aotz-- 2.07g                       0.00   11.52                            monitored

Configure Threshold for Auto-Extension

To set a threshold for auto-extension of the thin pool, edit the /etc/lvm/lvm.conf file. By default, the threshold is 100%, meaning the pool will not grow automatically. For example, setting the threshold to 75% will trigger an auto-extension when the pool reaches 75% capacity.

grep -E '^\s*thin_pool_auto' /etc/lvm/lvm.conf

thin_pool_autoextend_threshold = 100
thin_pool_autoextend_percent = 20

You may modify these values as needed:

• thin_pool_autoextend_threshold = 75
• thin_pool_autoextend_percent = 20

This configuration means the thin pool will auto-extend by 20% when it reaches 75% of its capacity.

Creating a Thin-Provisioned Volume for Local PV ZFS

To enable thin provisioning, set the thinProvision parameter to yes in the StorageClass definition. Refer to the StorageClass Parameters Documentation for more information.

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: puls8-zfspv
parameters:
  recordsize: "128k"
  compression: "off"
  dedup: "off"
  fstype: "zfs"
  poolname: "zfspv-pool"
  thinProvision: "yes"
provisioner: zfs.csi.openebs.io

Benefits of Thin Provisioning

• Over-provisioning of physical storage to create larger virtual volumes.
• Efficient use of available disk space.
• Flexibility to scale capacity based on actual usage.
• Cost-effective resource management.

Learn More

• Alerting
• Monitoring
• Eventing