We are building out new datacenters and I like the idea of booting from the HP internal SD card. Lights out datacenters seem to lend themselves to boot from SD or BFS to cut down on hardware calls. 80 hosts in 5 datacenters. I understand that /scratch will need to be configured and the HP provides only 1 SD slot. We have always booted from spinning disk or ssd. So how would our procedure differ? Install from HP iso, configure /scratch to point to a vmfs on our VNX, and off we go? Everything functions as we expect? If this is a huge complication in practice, I'd just a soon go to BFS.
Is this boot from SD common practice?
Sounds like you've got the only caveat covered.
It's handy to setup syslog and get such logs going there, but we've been running exactly that hardware on a reasonable number of hosts for a while without any issues.
We've got a bunch of enclosures of G7 blades booting off of SD cards, and bunch of remote sites booting off of USB sticks, and recently added 24 Gen8 blades booting from the microSD cards. They work fine with today's releases of ESXi - there were nasty issues several years ago that have since been fixed. We've also got some G7 AMD blades that have microSD cards and they work fine too (but why HP uses SD in a BL460c G7 but microSD in a BL465c G7 is beyond me).
Make sure you buy HP's microSD cards since they're the only ones that HP supports, and HP has been known to check. They're 10x the price of generic ones (and the generic ones do technically work) but the support helps justify the price.
It doesn't hurt to have an extra card on hand in case one you have dies - I've had one bad so far and HP will replace them under warranty but for the extra few bucks, a spare helps you get up faster.