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

It can be more straightforward to update the gmirror, however.  I've done
this with UFS --- old boot, pair of UFS/GMIRROR usb sticks that then boot
to a ZFS array that the BIOS couldn't see (so UFS only contained /boot and
/rescue).  It's easier to know that the boot is updated identically if
gmirrored.  Gmirror also has tools to verify, etc.

On Fri, Dec 1, 2023 at 7:46 PM 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.
>>
>>
>>