Comment # 17 on bug 932735 from Neil Brown

I created a test (virtual) system with two devices.
Each device I partitioned in 1G and 5G partitions

The 2 5G partitions I made into a RAID1 and put '/' there.
The 1G partition on the 'first' device was configure for swap.

I completed a minimal install. After the install, the system did not boot.

The boot loader has been placed on sdb only, not on sda.  And qemu tried to
boot from sda.  So that needs to be fixed.

But I don't think that is your problem you get as far as dracut so it must find
the boot loader.

So I told qemu that the devices were in a different order.  That booted fine.

Then I tried booting with only sdb (the device which has the boot loader
install).  That failed, though it got further - actually ran dracut.

It spent about 2 minutes waiting to find the other device (this is expected)
and then assembled the array.  But it still wouldn't boot.
The problem this time is that dracut was waiting for the swap partition to
appear, but it was on the missing device (sda).

I would suggest that if you want to be able to boot with one device missing,
then everything should be RAIDed, not just root.  Having swap on a device
requires that device to be present for boot (especially as it may be used for
hibernation).

I turned off swap, created a RAID1 of the two 1G partitions, mkswap on that,
updated /etc/fstab, ran "mkinitrd", then for good measure I ran "grub2-install"
on both /dev/sda and /dev/sdb

Now I can boot with either drive present - or with both.  If I shutdown with
both devices working and the boot with only one, there will be a 2 minute delay
which is expected, but it will work.

Could you try using a RAID1 for swap rather than an specific device, and see if
that works?