Hello,
On Sat, Sep 11, 2021 at 06:55:56PM +0200, Felix Natter wrote:
> How does d-i know how the individual HDDs were combined into a
> RAID1?
d-i doesn't as such. In Linux MD, member devices contain metadata to
allow assembly by udev. You can examine the data on an MD member
device like this:
$ sudo mdadm --examine /dev/sda1
/dev/sda1:
Magic : a92b4efc
Version : 1.2
Feature Map : 0x1
Array UUID : ae2dfc21:c73ccb97:24ca9476:e67c0532
Name : arran:0 (local to host arran)
Creation Time : Sat Dec 2 09:29:21 2017
Raid Level : raid1
Raid Devices : 2
Avail Dev Size : 3901440 (1905.00 MiB 1997.54 MB)
Array Size : 1950720 (1905.00 MiB 1997.54 MB)
Data Offset : 2048 sectors
Super Offset : 8 sectors
Unused Space : before=1968 sectors, after=0 sectors
State : clean
Device UUID : 0bfc69e4:8e62ef0b:b9c16b32:d7cee4f1
Internal Bitmap : 8 sectors from superblock
Update Time : Wed Sep 8 23:28:20 2021
Checksum : 3daa61a0 - correct
Events : 283
Device Role : Active device 0
Array State : AA ('A' == active, '.' == missing, 'R' == replacing)
This is how any system with Linux MD support can assemble and
manipulate your arrays given just the devices. Typically udev sees a
block device with MD metadata and calls the mdadm binary to
incrementally assemble it. Once enough devices have been seen the
array is functional.
Cheers,
Andy
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