u-boot & ZFS

[ChrisO]

On Wed, Aug 18, 2021 at 03:12:04PM +0100, Dimitri John Ledkov wrote:
> On Wed, Aug 18, 2021 at 2:26 PM ChrisO <armbian at osk.ch> wrote:
> >
> > On Wed, Aug 18, 2021 at 12:26:11PM +0200, Lukasz Majewski wrote:
> > > Hi ChrisO,
> > >
> > > > On Tue, Aug 17, 2021 at 08:35:14PM -0400, Tom Rini wrote:
> > > > > On Tue, Aug 17, 2021 at 06:03:10PM +0200, ChrisO wrote:
> > > > >
> > > > > > Hi
> > > > > >
> > > > > > I searched for u-boot ZFS references and all I found was several
> > > > > > years old, but I suppose u-boot can cope with ZFS. So, my
> > > > > > question is: is it possible to boot Linux from ZFS or at least
> > > > > > boot from let's say SD-card with ext4 FS and mount a ZFS volume
> > > > > > as root filesystem? I had a look at Armbian, installed all
> > > > > > needed, user-space and kernel modules. After booting from SD card
> > > > > > I can use ZFS on attached SATA SSD w/o any problem. I also see
> > > > > > ZFS libs and kernel modules in initrd,  so it looks like the
> > > > > > necessary things are there. Don't know where to start. I would be
> > > > > > very thankful for any help.
> > > > >
> > > > > The general easy answer is to have /boot that is separate from the
> > > > > rootfs and using a filesystem more commonly supported.
> > > > >
> > > > > --
> > > > > Tom
> > > >
> > > > Sounds like: go away kid, play with your old toys ;-)
> > > > I was doing it the traditional way for long time, now wanted to try
> > > > something new. Isn't it how we progress? I came to this list hoping
> > > > to get an answer to my question. I know, most of you on this list
> > > > have more important things to do. But giving me some advice could
> > > > possibly result in me giving something back.
> > > >
> > >
> > > Similar question I saw on OpenEmbedded/Yocto ML recenly. The answer
> > > there was that "ZFS or ZOL is _not_ [*] commonly used on embedded
> > > systems, so no support was needed"
> > >
> > > If find this topic interesting, then the community will try to help
> > > when you provide any patches for review.
> > >
> > > However, considering the above, it may be hard for any _exact_
> > > guidelines.
> > >
> > >
> > > Note:
> > > [*] - Personally, I didn't saw any usage of ZFS on embedded systems.
> > >
> > > > Thanks,
> > > > Chris
> > >
> > >
> > >
> > >
> > > Best regards,
> > >
> > > Lukasz Majewski
> > >
> > > --
> > >
> > > DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
> > > HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
> > > Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email: lukma at denx.de
> >
> > Hallo Lukasz
> >
> > My system in question is not an embeded one. I just stated to play with an Odroid-HC4 and Armbian.
> 
> 4GB of RAM sounds way too little for zfs.

Because ...
I don't want to keep my ZFS pool in RAM, it contains two disk partitions ~220GB and its usage of memory
for its cache, ARC (adaptive replacement cache) is:

root at odroidhc4:~# awk '/^size/ { print $1 " " $3 / 1048576 " MB" }' < /proc/spl/kstat/zfs/arcstats
size 5.91608 MB

I did administer, in another life ;-) large Solaris servers on ZFS only and never had mamory usage problems.

Thanks and regards,
Chris

> 
> > It has two SATA connectors, boots from a SD card.
> > All computer I use which have more than one disk connected are set-up with software RAID and LVM on top of it.
> > ZFS has both build-in it's why I asked.
> > Currently I have on this HC4 two partitions on each disk, the smaller ones are in RAID1 and host root FS, the bigger ones are in a mirrored Zpool. It works OK, it would be nicer to have just one filesystem, though.
> >
> > Still not sure, it can or cannot be done?
> >
> > Thanks and regards,
> > Chris
> 
> -- 
> Regards,
> 
> Dimitri.