For new installations of ESXi, during the autoconfiguration phase, a scratch partition is created on the installation disk if it is a high-endurance device such as a hard drive or SSD.
When ESXi boots, the system tries to find a suitable partition on a local disk to create a scratch partition.
The scratch partition is not required. It is used 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. In low-memory situations, you might want to create a scratch partition if one is not present.
The scratch partition is created during installation. Do not modify the partition.
If no scratch partition is created, you can configure one, but a scratch partition is not required. You can also override the default configuration. You can create the scratch partition on a remote NFS-mounted directory.