Re: EFI and zfs raid mirror partial fail (14.0 and RELENG_13)

On Fri, 1 Dec 2023 17:45:53 -0700
Warner Losh <imp@bsdimp.com> wrote:

> On Fri, Dec 1, 2023, 4:57 PM Pete French <pete@twisted.org.uk> wrote:
> 
> >
> > On 01/12/2023 21:53, mike tancsa wrote:
> > > Should have looked at open PRs. There is one from a while ago
> > >
> > > https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=258987
> > >
> > >
> >
> > Was thinking about this, and I was wondering if it would be possible to
> > make the EFI partition a gmirror. So its across all discs, mounted only
> > once, but would still boot from any of them. My understanding is geom
> > has the label at the end, yes ? So the firmware would see the filesystem
> > on a single partition quite happily ?
> >
> 
> I've done this. It works ok. But I don't run like this in production. If I
> write a new file, that has so many writes to the different disks. If they
> all go through then life is good (this is what gets us to OK).
> 
> BUT, if there is a power failure or crash and only some of them make it to
> disk, then you have a corrupt ESP and the BIOS may pick that ESP to boot
> off of, booting corrupt data.
> 
> Since this is infrequently updated, you can use a safe sequence to update
> things one partition a time, then you might lose the file entirely, but it
> will either be there and good. Or it will be gone. You can't get into a bad
> situation. Either you boot old or new loader and can just quit from the
> boot loader if it's the old one and it can't boot. Efi will try the next
> one on the list.
> 
> Here manual mirroring, if scripted, can be more reliable than gmirror.
> 
> Warner
> 
> -pete.

It looks reasonable if it is auto-generated by bsdinstall, used on
initial installation, and kept for later use by `make installworld`.

bsdinstall should know how many, and which disk is configured for
FreeBSD.

And, maybe impossible for now, but if "Actually booted from at this
time" ESP is auto-mounted on default location, it could be helpful for
admins. Just a thought.

-- 
Tomoaki AOKI    <junchoon@dec.sakura.ne.jp>