Storage Requirements for ESXi 5.0 Installation
Installing ESXi 5.0 requires a boot device that is a minimum of 1GB in size.
When booting from a local disk or SAN/iSCSI LUN, a 5.2GB disk is required to
allow for the creation of the VMFS volume and a 4GB scratch partition on the
boot device. If a smaller disk or LUN is used, the installer will attempt to
allocate a scratch region on a separate local disk. If a local disk cannot be
found the scratch partition, scratch, will be located on the ESXi host ramdisk,
linked to /tmp/scratch. You can reconfigure scratch to use a separate disk
or LUN. For best performance and memory optimization, VMware recommends that
you do not leave scratch on the ESXi host ramdisk.
To reconfigure /scratch, see Set the Scratch Partition from the vSphere Client.
Due to the I/O sensitivity of USB and SD devices the installer does not create a
scratch partition on these devices. As such, there is no tangible benefit to using
large USB/SD devices as ESXi uses only the first 1GB. When installing on USB
or SD devices, the installer attempts to allocate a scratch region on an available
local disk or datastore. If no local disk or datastore is found, /scratch is
placed on the ramdisk. You should reconfigure /scratch to use a persistent
datastore following the installation.