With vSphere 7 Update 3 came bad news for all users who use USB flash media or SD cards as ESXi boot device. I have described the changes in the partitioning of the boot device in the article “ESXi Bootmedia – New features in v7 und legacy issues from the past v6.x“.
The discontinuation of support for SD cards and USB boot media put many customers in the uncomfortable position of having to replace their boot media on existing servers. VMware has responded by resuming support for SD cards and USB media under certain criteria.
The problem with these media remains. The wear of these storages was worked around by swapping out write-intensive areas. Since update 7.0 U3c, the setup detects an installation on SD/USB devices and tries to swap critical areas of the OSData partition to more stable media. This for instance includes VM-Tools and Scratch. Starting with the upcoming vSphere.Next release, the entire OSData partition will be swapped out to more robust data storage. However, the question arises here why, when resilient storage media is available, it is not used completely as a boot device right away.
VMware has published details about the changed strategy concerning boot media in KB 85685.