Invalid RAID superblock magic on a partition not in a RAID

ghughes5669 · 03-31-2016, 02:32 PM

Good afternoon, all!

Ran across an interesting message that flashed across one of my servers:
md: invalid raid superblock magic on sdb1

Interesting because sdb1 is not a part of a RAID.

My setup is to have mirrored disks, with sda1 and sdb1 the boot partitions - not mirrored, and sda2/sdb2 as root and sda3 and sdb3 as swap.

If there's an invalid superblock magic on a partition not managed by mdadm, what might md be complaining about?

Thanks to all for looking!

Gregg

rknichols · 03-31-2016, 03:42 PM

If the partition type is 0xfd (Linux raid auto) then the kernel is going to try to build a RAID array using it.

ghughes5669 · 03-31-2016, 03:59 PM

Hello, RK!

I checked and that is indeed the case. I have absolutely no idea where that system came from.

A couple of follow-up questions arise: is there any mileage to be gained by fixing this? Second, fdisk shows both the sda1 and sdb1 partitions as bootable. Given that, is it worth the downtime to chase this down?

Thanks for the info!

Gregg

rknichols · 03-31-2016, 04:34 PM

The "active" (boot) flag is irrelevant to Linux boot loaders, though some BIOS variants won't consider a drive to be a boot candidate if there is no partition marked "active".

If you are not using /dev/sdb1 in a RAID array, just run "fdisk /dev/sdb" and change the type for partition 1 to something more suitable, perhaps "83" (Linux). Then you will no longer see that message when you boot.