ESXi System Storage FAQ


This article details frequently asked questions and answers about vSphere ESXi core storage, including Auto Deploy and vLCM.

ESXi System Storage

What has changed for ESXi system storage?

We have increased the boot bank sizes, and consolidated the system partitions and made them expandable. This article details these changes introduced with vSphere 7 and how that reflects on the boot media requirements to run vSphere 7.

What happens to the system storage layout when I upgrade my ESXi hosts to vSphere 7?

The ESXi system storage requirements are also applicable for ESXi upgrades (6.x > 7). However, the boot media requirements differ between a new vSphere 7 install, and an upgrade to vSphere 7. There’s a requirement for boot media to run a 4 GB storage device at minimum, when upgrading to vSphere 7.  Even though 4 GB boot media devices are supported, it is strongly recommended to adhere to the boot media requirements for a fresh vSphere 7 installation. Check out this article for detailed information.

What is recommended for ESXi system storage?

Looking ahead, there will be new features that require ESXi hosts with high-quality local storage. The recommended ESXi 7.0 install options are the following:

  • An 8 GB USB or SD and an additional 32 GB local disk. The ESXi boot partitions reside on the USB or SD and the ESX-OSData volume resides on the local disk.
  • A local disk with a minimum of 32 GB. The disk contains the boot partitions and ESX-OSData volume.
  • A local disk of 142 GB or larger. The disk contains the boot partitions, ESX-OSData volume, and VMFS datastore.

Are USB/SD boot devices being deprecated?

No. USB-based boot interfaces are not deprecated. However, VMware encourages the use of local storage media like flash (NVMe/SSD), HDD, or M.2 for boot because of reliability concerns as outlined in the "ESXi 7.0 Installation on M.2 and Other Non-USB Low-End Flash Media" section of this article.

Degraded Mode

Why do I see my ESXi hosts are running in 'Degraded Mode'?

When ESXi hosts are booted from a USB or SD device, and are not equiped with an additional local HDD or Flash media (NVMe or SSD) to store the OSData partition, ESXi goes into degraded mode because the USB/SD device isn't used for logs or persistent storage. Partitioning for hosts that are upgraded to ESXi 7 from earlier versions differs significantly from partitioning for new installations of ESXi. The size of bootbank partitions is different and autoconfiguration might not configure a coredump partition on the boot disk due to size limitations.

When in degraded mode, a sysalert is shown:  "ALERT: No persistent storage available for system logs and data. ESX is operating with limited system storage space, logs and system data will be lost on reboot."

What does Degraded Mode mean?

Degraded mode, in summary, is a state where logs and state might not be persistent (get lost when the host is rebooted), with a side effect that it can cause boot up to be slower.

With new features and capabilities like vSphere Lifecycle Manager, vSAN, and NSX-T, the way VMware approaches ESXi host installations have changed. More and more features and capabilities will rely on host local storage for additional kernel modules, but also for state information like PCIe mappings and SSL certificates.

Can I add local storage after I upgrade to ESXi 7?

Yes. It is good practice to equip ESXi hosts with recommended local storage media. When adding local storage after upgrading to ESXi 7,  enable the advanced setting autoPartition=TRUE and reboot the ESXi hosts as described in KB article 77009 to mitigate degrade mode.

I can't retrofit local storage media, how do I mitigate?

If local storage is not present and the ESXi host is running in Degraded Mode, there's still ways to make sure logs are stored, by using external Syslog solutions, NetDump Collector or Core Dump Partition. See this article how to enable Syslog on ESXi hosts.

Auto Deploy

I’m using Auto Deploy, what do I do?

vSphere Autodeploy is fully supported. However, with the recommendation to use ESXi host local storage for new features and capabilities, it is recommended to (re)configure the Host Profiles with Auto Deploy to use Stateful Installs. Doing so does require local storage for the ESXi hosts.

vSphere Lifecycle Manager (vLCM) is a new feature that relies on local storage. When vLCM is used in an environment with Auto Deploy, customers should change to statefull installations, see this article for more details.

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