using SSD on RPI3 - strategy question

[Greg Troxel <gdt%lexort.com@localhost>]

I have a RPI3, with system on uSD, and an USB spinning disk for data,
both because what I am storing/writing won't fit and to avoid wear from
writing.  I got a smallish USB SSD to replace the spinning disk, and I
am wondering how to set it up.

It seems that the boot partition must be FAT32 on the uSD, to read the
kernel.  I'm not trying to fight that.  But if it's possible to boot
from external USB SSD with no uSD, that would be nice.  My impression is
that this sort of should work, and probably needs the same kind of disk
layout on the SSD as the uSD.

On this system, I expect to always have the SSD, and given what it's
doing, it's not really useful without it.

One option is to have the operating system on uSD, and mount the
external disk on /d1 and put big/often-written stuff there, as I'm doing
now.

A middle ground is to have a small / on the uSD, but mount /usr and /var
on the SSD.  This doesn't seem useful if the next option actually works.

Another option is to change the boot config to have the root filesystem
on the SSD.

So I am leaning to formatting the SSD as GPT, making a 16G root, using
that like the uSD was, and the rest as /d1 for bulk data, so that the
uSD is only written for kernel updates, and presumably the SSD will last
longer.



I don't see any discussion of this in the wiki.  Advice welcome, and if
there's a clear view on anything, I can spiff up the wiki