> 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/zh/storage-vsan/preferred-tier-usage.md).

# 首选层级的使用

在 VergeOS 中创建或修改虚拟机（VM）磁盘驱动器时，用户可以设置一个 **首选层级**。在大多数情况下，这会保持为 **默认**，可在以下位置配置 **系统 > 系统设置 > 默认 VM 驱动器层级**。不过，当指定的层级不存在时，系统的行为可能出乎意料。以下是 VergeOS 在这种情况下如何确定使用哪个层级：

* **将首选层级设置为不存在的更高层级**:
  * 例如：如果用户选择 **第 3 层** ，而系统只有 **第 1 层** 以及 **第 4 层** 可用存储，系统将尝试选择下一个更高（更慢）的层级。在这种情况下，系统将默认使用 **第 4 层**.
* **将首选层级设置为不存在的更低层级**:
  * 例如：如果用户选择 **第 3 层** ，而系统只有 **第 1 层** 以及 **第 2 层** 存储，系统将选择下一个更低（更快）的层级。在这种情况下，系统将默认使用 **第 2 层**.

在这两种情况下，VergeOS 都会根据用户的偏好选择最接近的可用层级。

***

{% hint style="info" %}
**文档信息**

* 最后更新：2024-08-29
* vergeOS 版本：4.12.6
  {% endhint %}


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