Re: [gentoo-user] Fun with mdadm (Software RAID)

[Wols Lists <antlists@youngman.org.uk>]

On 20/12/2024 20:19, Alan Mackenzie wrote:
> I've just tried it, with metadata 1.2, and it doesn't work.  I got error
> messages at boot up to the effect that the component partitions were
> lacking valid version 0.0 super blocks.
> 
> People without initramfs appear not to be in the sights of the
> maintainers of this software.  They could so easily have made the
> assembly of metadata 1.2 components on the kernel command line work.
> 🙁
No they couldn't. Not if they wanted (at the time) a kernel small enough 
to boot successfully ...

Making the disk write write identically to two disks (your basic 0.9 
mirror) is pretty simple, and also extremely error prone. Making mdraid 
robust with all the other features of an enterprise "protect your data" 
system is a lot more work.

mdraid has probably just protected my data - dunno what triggered it, 
but I lost a disk and it just got rebuilt in the background without me 
doing a thing ...
> 
> By the way, do you know an easy way for copying an entire filesystem,
> such as the root system, but without copying other systems mounted in
> it?  I tried for some while with rsync and various combinations of
> find's and xargs's, and in the end booted up into the rescue disc to do
> it.  I shouldn't have to do that.

Provided it's read-only (so yes if it's the root I might well use a 
rescue disk) I'd use dd. That's assuming a fairly small root that's 
fairly full, it's rather wasteful if it's not ...

Cheers,
Wol