Re: Redundancy for EFI System Partition: what do people do in 2020?
[ Adding CC to the debian-efi list too... ]
Hey Andy!
Andy Smith wrote:
>
>More of my adventures in EFI land.
>
>Machines that boot by EFI need an EFI System Partition. I'm used
>to using software RAID everywhere and providing redundancy for
>everything. It seems that the designers of EFI didn't think about
>that one.
>
> https://www.tinkerfairy.net/efi-raid.txt
> https://www.claudiokuenzler.com/blog/696/uefi-efi-boot-does-not-like-software-raid-system-partition-grub-error-17
>
>https://unix.stackexchange.com/questions/265368/why-is-uefi-firmware-unable-to-access-a-software-raid-1-boot-efi-partition
>
>So, those of you who boot by EFI and use software RAID, how do you
>choose to provide redundancy for your ESP any why did you make that
>choice?
>
>I understand the main choices are:
>
>a) Don't provide redundancy.
>
> There's only one ESP. If the device it's on dies you can recreate
> it with a live environment such as the rescue mode of the
> installer.
And obviously it's the only option when you're on a single-disk system
like a laptop.
>b) Put the ESP in a v1.0 mdraid level 1.
>
> As the RAID metadata is at the end, it appears to the firmware
> like a normal filesystem for read purposes. Updating it from
> within the OS writes to both copies as it's a RAID-1.
>
> Has the risk that if the firmware writes to it (which apparently
> it sometimes does), it will corrupt the RAID.
ACK. That's my worry here. Also, currently grub-install gets upset
when you try to install to a "disk" that the underlying firmware
doesn't understand and so can't add a boot record (as I think is
mentioned in your links above). So you have to install to the
removable media fallback path too.
I've gone that way on the machine I'm typing this on for *now*. It's
on my TODO list to hack on grub-install to do something better here
(i.e. recogonise the RAID, work out which disks are involved, and then
add boot records for each) but I'm struggling with time to do that
atm. *So* many projects, so little time. :-(
>c) Manually sync the ESP to another partition which can be used if
> the first device dies.
>
> An identical partition can be created on the second device and an
> arrangement made to copy the real ESP to the secondary partition
> every time grub-install would be run.
>
> You would have to be sure that this is as automated and foolproof
> as possible, to avoid being lulled into a false sense of security
> and then have a problem at the worst time.
Yup, that's the other option that might make sense. It's not
wonderful, but could likely be scripted easily enough. I've been doing
this manually (i.e. badly!) from time to time on the house server.
>d) Something else?
Another option if you're feeling keen/brave would be to write an EFI
driver for Linux SW RAID. I'd expect the EDK2 folks would be very
happy if somebody wanted to do that...
I had a conversation a few years back with some guys at one large PC
vendor who were apparently considering adding firmware support like
this. Then things went quiet and I can only assume it's not
coming from them...
--
Steve McIntyre, Cambridge, UK. steve@einval.com
"You can't barbecue lettuce!" -- Ellie Crane
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