When you install ESXi or use Auto Deploy to provision hosts, you can enable the auto-partitioning boot option to create partitions on your host. You have several options to prevent auto-partitioning from formatting local SSDs as VMFS.
By default, auto-partitioning deploys VMFS file systems on any unused local storage disks on your host, including SSD disks.
However, an SSD formatted with VMFS becomes unavailable for such features as virtual flash and Virtual SAN. Both features require an unformatted SSD and neither can share the disk with any other file system.
To use auto-partitioning and to ensure that local SSDs remain unpartitioned, use the following boot options when you install ESXi or boot the ESXi host for the first time:
If you use Auto Deploy, set these parameters on a reference host.
In the vSphere Web Client, select the host to use as a reference host and click Manage.
Click System to open the system options, and click Advanced System Settings.
Scroll to VMkernel.Boot.autoPartition and set the value to true.
Scroll to VMkernel.Boot.skipPartitioningSsds and set the value to true.
Reboot the host.
If SSDs that you plan to use with Flash Read Cache and Virtual SAN already have VMFS datastores, remove the datastores.