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Re: mdadm and whole disk array members



On 2021-03-23 11:45, Reco wrote:
	Hi.

On Tue, Mar 23, 2021 at 01:44:23PM +0100, deloptes wrote:
IMO the problem is that if it is not a partition the mdadm can not
assemble as it is looking for a partition,
My mdadm.conf says:

# by default (built-in), scan all partitions (/proc/partitions) and all
# containers for MD superblocks. alternatively, specify devices to scan,
# using wildcards if desired.
#DEVICE partitions containers


And /proc/partitions always had whole disks, their partitions, lvm
volumes and whatever else can be presented as a block device by the
kernel.
So mdadm is perfectly capable of assembling whole disk arrays, and it
does so for me for more than 10 years.

but not sure how grub or whatever handle it when you boot off the
drive.
GRUB2 can definitely boot from mdadm's RAID1 as it has an appropriate
module for this specific task. Installing GRUB2 on mdadm array made of
whole disks is tricky though.

UEFI itself, on the other hand - definitely can not, unless you resort
to some dirty hacks. After all, UEFI requires so-called "EFI System
Partition" aka ESP.

Reco

From what I read in looking for solutions, the problem is common. I even tried one workaround of zapping any existing partition table on the drives. Nothing worked.

Perhaps it only works with virgin drives? Mine had been removed from another machine where they had been part of a different array. I zeroed the superblocks before creating the new array.


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