Raid 1 in HPE Gen10

[Sam Varshavchik]

Robert Moskowitz via ubuntu-users writes:

> I have an HPE Gen 10 with 4 4TB drives that has been sitting for 2 years for  
> me to figure out how to get RAID working.
>
> Now that I am working with Ubuntu, it almost makes sense, but I am not  
> there.  Yet.
>
> Seems I have to go into custom setup for the drives.
>
> So far I have only taken 2 drives into a RAID1 config and the other two into  
> an LVM
>
> Once I selected Raid and put the two drives in it, I was only offered  
> formatting as EXT4 for /
>
> I am being told I need a boot partition.  Of course.
>
> So is there any decent guide for this?

It is certainly possible because I have done this exact same thing, but  
using mdraid rather than any hardware-based RAID. A lot of ink has been  
spilled about this, over the years, but the capsule summary is that mdraid  
over the long term will fare better. You can pull the disks and drop them  
into another box and it'll just work, for example. You can't do this with  
hardware RAID, without also installing identical hardware, too. And if your  
hardware RAID card gives up the magic smoke you're SOL, unti you can find an  
identical replacement.

I basically followed this:

https://askubuntu.com/questions/1299978/

but skipped some of the fluff up front. The capsule summary is:

1) Boot the installer, open a terminal shell

2) apt update, apt install mdadm

3) Use fdisk (or sgdisk) to partition both drives, then use mdadm to  
assemble them into RAID arrays.

This is where I wish I've done something different than the guide, which  
basically tells you that the EFI boot partition is SOL, as far as mdraid  
goes, and gives you marching orders to just create a non-RAID partition on  
both disks, use the one on the boot drive for the UEFI partition, set up  
some automation to dd it to the other drive's partition, and use efibootmgr  
to include both disks as bootable devices.

Since then, I've learned that it should be possible to use mdraid for the  
EFI boot partition by formatting it as mdraid 1.0 instead of mdraid 1.1  
(still need to fiddle with efibootmgr). It just so happens that this is  
exactly the situation on my other box running Fedora, which has no issues  
with the efi boot partition on mdraid (Fedora's installer directly supported  
installation to mdraid for a very long time, at least a decade). I'll try  
that next time.

3) Start the ubuntu installer. It'll be slightly confused and list both the  
physical partitions and the RAID partition together, as installation  
targets. Be sure to select the right partitions (disclaimer, this was the  
story in Ubuntu 20, current experience might vary).

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