Karl Denninger karl at denninger.net
Fri Feb 22 15:54:23 UTC 2019

On 2/22/2019 09:38, Stefan Parvu wrote:
> I know ZFS would need a decent amount of RAM to start with. So for such low sized 
> SBC systems, like Raspberry PI having ZFS for root might be no go.
> What I meant was: how complicated would be right now for FreeBSD 12 to have an 
> ARM64 RBPI3B+ image image which could use ZFS to boot from a SD Card.
> Stefan Parvu
> sparvu at kronometrix.org

I'm trying to figure out the use case.

Will it boot?  Probably.  Is it asking for trouble?  Almost-definitely.

SD cards are not write-durable to begin with.  I use NanoBSD-style
configurations on these units because I've had *several* SD card
failures over the last few years in them, which were only halted when I
stopped treating them the same way I'd look at either a traditional SSD
or spinning rust, just slower.  I suspect ZFS is only going to amplify
that problem -- maybe by a lot.

It's easy enough to figure out whether the base case will run; boot the
traditional media and then issue a "zfs" command so the .ko files come
in and then see what sort of free RAM you have.  If it crashes instantly
you have your answer, but I would expect it, at that level, to "work" --
you can then set up a pool on a USB-attached disk and see how that
goes.  The issue is that without swap (and swapping to an SD card is an
insanely bad idea) RAM pressure results in killed jobs so the
next-obvious question is what do you want to run on the Pi once it's
booted and running?  You're taking on a pretty decent amount of overhead
so the question becomes "for what purpose?"

If I get some time I'll play with it here (I use the Pis for embedded
work on FreeBSD fairly heavily but right now am in the middle of some
build work that precludes me from doing it today) but I'm having trouble
envisioning why you'd want a zfs root on a Pi to begin with.

Karl Denninger
karl at denninger.net <mailto:karl at denninger.net>
/The Market Ticker/
/[S/MIME encrypted email preferred]/
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