Storage

The following article provides insides about the different kinds of storage used in Kubernetes clusters.

Worker storage

Used by the worker machines as local storage.
It is used for:

• booting the worker machine with the specified Operating system
• fetching and saving container images
• ephemeral storage (for example, emptyDir volumes).
• hostPath

Calculation

Storage is calculated with two factors. Disks per hour (D/h) and Gigabytes per hour (GB/h).

If the cluster stays at a scale of 3 nodes (no auto-scaling triggers) and therefore uses 3 root disks of the same storage class with 50 GB each the whole month, the storage costs are calculated as follows (calculation is based on 730 hours for a month):

=> 3 * (50 GB * 730h + 730h * 1 Disk)
=> 3 * (36500 GBh + 730 Dh)
==> 109500 GBh + 2190 Dh

PVCs

Inside your cluster you can provision STACKIT Block Storage volumes automatically with the creation of a PVC.

After applying a Persistent Volume Claim (PVC) with a specified size and StorageClass, SKE will automatically create a STACKIT block storage volume and a corresponding Persistent Volume (PV). The storage will be mounted to a pod if specified Claim PVs as Volumes. Be aware that block storage can only be mounted to one node at a time. RWX Volumes are currently not supported.

The default reclaim-policy of the Persistent Volume (PV) is set to DELETE, so if the PVC is deleted the corresponding STACKIT block storage volume will also be deleted. This can be changed by configuring of the StorageClass (refer to Kubernetes-reclaim-policies).

Calculation

Given you have an application that requires three 10 GB Volumes and one 500 GB Volume and runs for the whole month (730h), the costs are calculated as follows:

=> (3 * 10 GB * 730h + 730h * 3 Disk) + (500 GB * 730h + 730 * 1 Disk)
=> (3 * 7300 GBh + 730h * 3 Disk) + (365000 GBh + 730h * 1 Disk)
=> (21900 GBh + 2190 Dh) + (365000 GBh + 730 Dh)
==> 386900 GBh + 2920 Dh