ESXi 8.0 has a system storage layout that allows flexible management of partitions and third-party components, while facilitating debugging.
ESXi System Storage
| Partition | Use | Type |
|---|---|---|
| System Boot | Stores boot loader and EFI modules. | FAT16 |
| Boot-bank 0 | System space to store ESXi boot modules. | FAT16 |
| Boot-bank 1 | System space to store ESXi boot modules. | FAT16 |
| ESX-OSData | Acts as the unified location to store additional modules. Not used for booting and virtual machines. Consolidates the legacy /scratch partition, locker partition for VMware Tools, and core dump destinations.
Caution: In case the installation media is a USB or an SD card device, best practice is to create ESX-OSData partitions on persistent storage device that is not shared between ESXi hosts.
|
VMFS-L |
The ESX-OSData volume is divided into two high-level categories of data, persistent and non-persistent data. Persistent data contains of data written infrequently, for example, VMware Tools ISOs, configurations, and core dumps.
Non-persistent data contains of frequently written data, for example, logs, VMFS global traces, vSAN Entry Persistence Daemon (EPD) data, vSAN traces, and real-time databases.
ESXi System Storage Sizes
Partition sizes, except for the system boot partition, can vary depending on the size of the boot media used. If the boot media is a high-endurance one with capacity larger than 142 GB, a VMFS datastore is created automatically to store virtual machine data.
You can review the boot media capacity and the automatic sizing as configured by the ESXi installer by using the vSphere Client and navigating to the Partition Details view. Alternatively, you can use ESXCLI, for example the esxcli storage filesystem list command.
| Boot Media Size | 8-10 GB | 10-32 GB | 32-128 GB | >128 GB |
|---|---|---|---|---|
| System Boot | 100 MB | 100 MB | 100 MB | 100 MB |
| Boot-bank 0 | 500 MB | 1 GB | 4 GB | 4 GB |
| Boot-bank 1 | 500 MB | 1 GB | 4 GB | 4 GB |
| ESX-OSData | remaining space | remaining space | remaining space | up to 128 GB |
| VMFS datastore | remaining space for media size > 142 GB |
systemMediaSize to limit the size of system storage partitions on the boot media. If your system has a small footprint that does not require the maximum of 128 GB of system storage size, you can limit it to the minimum of 32 GB. The
systemMediaSize parameter accepts the following values:
- min (32 GB, for single disk or embedded servers)
- small (64 GB, for servers with at least 512 GB of RAM)
- default (128 GB)
- max (consume all available space, for multi-terabyte servers)
The selected value must fit the purpose of your system. For example, a system with 1 TB of memory must use the minimum of 64 GB for system storage. To set the boot option at install time, for example systemMediaSize=small, refer to Enter Boot Options to Start an Installation or Upgrade Script. For more information, see Knowledge Base article 81166.
ESXi System Storage Links
| System Storage Volume | Symbolic Link |
|---|---|
| Boot-bank 0 | /bootbank |
| Boot-bank 1 | /altbootbank |
| Persistent data | /productLocker /locker /var/core /usr/lib/vmware/isoimages /usr/lib/vmware/floppies |
| Non-persistent data | /var/run /var/log /var/vmware /var/tmp /scratch |
Storage Behavior
When you start ESXi, the host enters an autoconfiguration phase during which system storage devices are configured with defaults.
When you reboot the ESXi host after installing the ESXi image, the host configures the system storage devices with default settings. Starting with ESXi 7.0, you can activate the option autoPartition, which automatically formats all available empty devices with VMFS, except for legacy SD and USB devices. The default is autoPartition=FALSE, which formats with VMFS only boot devices with size larger than 128 GB. For more information, see VMware knowledge base article 77009.
On the hard drive or USB device that the ESXi host is booting from, the disk-formatting software retains existing diagnostic partitions that the hardware vendor creates. In the remaining space, the software creates the partitions described below.
Partitions Created by ESXi on the Host Drive
For fresh installations, several new partitions are created for the system boot, boot banks, and ESX-OSData. Fresh ESXi installations use GUID Partition Tables (GPT) instead of MSDOS-based partitioning. The installer creates boot banks of varying size depending on the size of the disk. For more information on the scratch partition see About the Scratch Partition.
The installer affects only the installation disk. The installer does not affect other disks of the server. When you install on a disk, the installer overwrites the entire disk. When the installer autoconfigures storage, the installer does not overwrite hardware vendor partitions.
To create the VMFS datastore, the ESXi installer requires a minimum of 128 GB of free space on the installation disk.
- Before you start the host for the first time.
- Before you start the host after you reset the host to the configuration defaults.
To override the VMFS formatting if automatic disk formatting already occurred, you can remove the datastore. See the vCenter Server and Host Management documentation.
About the Scratch Partition
For new installations of ESXi, during the autoconfiguration phase, a scratch partition is created as part of the ESX-OSDATA partition.
The scratch partition serves to store system logs, which you need when you create a support bundle. If the scratch partition is not present, system logs are stored in a ramdisk. If no scratch partition is created, you can configure one. You can also override the default configuration.
You can create the scratch partition on a remote SAN or NFS-mounted directory.
Set the Scratch Partition from the vSphere Client
If a scratch partition is not set up, you might want to configure one, especially if the host is low on memory. When a scratch partition is not present, system logs are stored in a ramdisk.
Prerequisites
The directory to use for the scratch partition must exist on the host.
