> For the complete documentation index, see [llms.txt](https://docs.verge.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.verge.io/knowledge-base/storage-vsan/preferred-tier-usage.md).

# Preferred Tier Usage

Explains how VergeOS determines which vSAN storage tier to use when a VM disk's preferred tier is set to a non-existent tier, including fallback behavior.

When creating or modifying a virtual machine (VM) disk drive in VergeOS, users can set a **Preferred Tier**. In most cases, this is left at **default**, which can be configured under **System > System Settings > Default VM Drive Tier**. However, the system's behavior when a specified tier does not exist can be unexpected. Here's how VergeOS determines which tier to use in such cases:

* **Setting a preferred tier to a non-existent higher tier**:
  * Example: If a user selects **Tier 3** in a system that only has **Tier 1** and **Tier 4** storage available, the system will attempt to pick the next higher (slower) tier. In this case, the system will default to **Tier 4**.
* **Setting a preferred tier to a non-existent lower tier**:
  * Example: If a user selects **Tier 3** in a system that only has **Tier 1** and **Tier 2** storage, the system will pick the next lower (faster) tier. In this case, the system will default to **Tier 2**.

In both scenarios, VergeOS ensures that the closest available tier is selected based on the user’s preference.

***

{% hint style="info" %}
**Document Information**

* Last Updated: 2024-08-29
* vergeOS Version: 4.12.6
  {% endhint %}


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