Hi,
that is normal as - if you like you can create a persistent area for the scratch partition http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1033696
From VMware documentation
"Installing ESXi 5.1 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."