With ESXi 7.0 Update 1c, you can use the installer boot option 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 138 GB system-storage size, you can limit it to the minimum of 33 GB. The systemMediaSize parameter accepts the following values:
min (33 GB, for single disk or embedded servers)
small (69 GB, for servers with at least 512 GB RAM)
default (138 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 1TB of memory must use the minimum of 69 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 VMware knowledge base article 81166.