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

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.
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