On 2020-12-30 13:38, Andy Smith wrote:
Hi Mick,
On Tue, Dec 29, 2020 at 03:32:07PM +0000, mick crane wrote:
On 2020-12-29 13:10, Andy Smith wrote:
>The default metadata format (v1.2) for mdadm is at the beginning of
>the device. If you've put a filesystem directly on the md device
>then the presence of the metadata will prevent it being recognised
>as a simple filesystem. What you can do is force mdadm to import it
>as a degraded RAID-1.
<..>
I've puzzled about this. Are you supposed to have 3 disks ?
One for the OS and the other 2 for the raid1 ?
It's unclear to me how what you have quoted relates to your
subsequent question. Can you elaborate on what the location of mdadm
metadata has to do with whether one puts the operating system on a
RAID-1 device or not?
I expect that most people using RAID put their OS into the RAID as
well. I certainly do. I don't understand your mental separation of
"OS" and "RAID-1" or why it might mandate 3 devices. It is perfectly
straightforward to put a single partition¹ on each of two devices,
RAID-1 them together and use it as root filesystem and that's it.
Probably we are just misunderstanding each other and there is a
question here that I haven't understood.
I just confused myself. Initially I read somewhere that to make the raid
first copy the OS from one disk to another.
Just struggling to get a picture of what happens, if what's on one disk
gets copied to the other or if they are written to simultaneously.
I always understood that you can't duplicate one disk to another with
itself being the OS.
It'll be the way the software raid does it. I should probably read more.
mick
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