While chatting with a sysadmin colleague of mine about setting up a small server for me, I found out something interesting - most servers these days apparently contain an internal USB port which can be used for attaching a boot flash drive. On one hand this makes sense - the OS doesn't need to use its disk much, and all the data is being kept on actual fast hotswap drives. We've successfully eliminated the need for an extra drive bay.
On the other hand - flash drives? Really? Is this safe? Seems so weird. Is this really common practice today?
It is pretty common practice today, especially for virtualization hosts (ESXi, Hyper-V, etc.).
Standard server often come with OEM OS on flash card. It's usually on MicroSD card.
Often you can mirror it too, as you can have two SD card on the controller.
On the other side the most practical use is for having a hypervisor on it, like ESX. The hypervisor, even if it crash can leave other server in the pool handle the VM witgh a proper HA configuration, and re-installing a ESX inside a SD card take 30m in the worst case.
I would be careful to do a flash setup if it's a standalone scenario.
We have thousands of servers running VMware's ESXi off SD cards, I believe you can also run Photon Linux and possibly Windows Nano off SD/USB cards too.