mdadm not showing RAID info on individual RAID array disks

Question

I am testing the mdadm Linux tool in order to obtain metadata from each individual disk of a RAID array.

So I have created a RAID array on a IBM Server (model IBM X3400 Dumpster Server, a Xeon E5410 Quadcore) using its own RAID controller (Adaptec). The array was created via BIOS tool (Ctrl+A when booting), named "IBM ServeRAID Configuration Utility" (well, not a very detailed tool, rather basic, but enough for me, I would say).

The configuration data for this newly created array is:

• RAID type: 5
• 4 x 500GB Hard Disk
• Chunk size (named strip size): 256 KB

System boots OK (using a common Ubuntu live distro), and now I can see a unpartitioned 1.3TB disk, as expected.

To test mdadm, I have extracted one of the 5x500GB disks, and plugged it (USB) on another computer running Ubuntu Linux (v20).

This is the output from fdisk :

$ sudo fdisk -l /dev/sdd
Disk /dev/sdd: 465.78 GiB, 500107862016 bytes, 976773168 sectors
Disk model: ASM1156-PM
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 33553920 bytes

And this is the output from mdadm :

luis@xubuntu:~$ sudo mdadm --examine /dev/sdd
mdadm: No md superblock detected on /dev/sdd.
luis@xubuntu:~$ sudo mdadm --examine /dev/sdd1
mdadm: cannot open /dev/sdd1: No such file or directory

What am I doing wrong?
Isn't mdadm supposed to yield metadata details (as shown here ) of the RAID Array on individual disks?
Maybe mdadm can not work with all RAID structures, and I am needing for another tool?

Of course, there are no partitions defined on `/dev/sdd' and so on, but I don't think they should be needed to get RAID details.

Answer 1

You're confusing hardware RAID (for some value of hardware) with software RAID. The mdadm tool manages soft(ware) RAID and understands some of the industry RAID container formats. It doesn't manage hardware RAID, as created by your Adaptec card

You may be able to get a utility suite that allows you to query the state of the disks but I would imagine it's unlikely to be through mdadm

Answer 2

mdadm is mostly for working with software RAIDs created by mdadm. It supports some BIOS RAIDs, mostly DDF (Disk Data Format) and ISMS (Intel Matrix Storage Manager) formats, but this is relatively new feature and not all BIOS RAIDs are supported. Some other BIOS RAIDs are supported by DM RAID, but again not all of them. If you have a hardware RAID controller, this needs to be managed by a special software specific for that controller (usually) and the resulting RAID array will be visible as a single "normal" disk in the system, not as an array and mdadm can't be used to get information about it.