How to mount a disk from destroyed raid system?

If you possibly can you should make a dd image of your entire disk before you do anything, just in case.

You should be able to mount /dev/sda3 directly once mdadm releases it:

mdadm --stop /dev/md2

mount /dev/sda3 /mnt/rescue

If that doesn't work testdisk can usually find filesystems on raw block devices.

I did it by the "hard way": (first if its possible clone this disk before you do anything!)

dmesg for the raid-disk or try (example: sdc1)

$ fdisk -l

Change the RAID-DISK-Flag to your Linux filesystem (ext3 or something), save this and reboot.

After that

$ mdadm --zero-superblock /dev/sdx 

and voila you can mount

$ mount /dev/sdc1 /mnt

In my case I brought up CentOS 7 and tried following everyone's instructions on this page. I kept running into a device busy message. The reason in my opinion why you are getting the

mdadm: cannot open device /dev/sda1: Device or resource busy

error message is because the device is already mounted as something else.

I also did not want to make any changes to the disk at all since my use case was to extract a very large file from my RAID1 array that failed to be extracted every possible way otherwise and the fastest way was to pull one of the drives out, I do want to put the drive back in and still have my configuration in place as well.

Here is what I did after doing some online research on other sites: NOTE: NAS:0 is the name of my NAS device so substitute appropriately.

It was automatically mounted although it would say that its not mounted if you were to run the mount command, you can verify that it was mounted by running:

[root@localhost Desktop]# cat /proc/mdstat 
Personalities : [raid1] 
md127 : active (auto-read-only) raid1 sdb2[0]
      1952996792 blocks super 1.2 [2/1] [U_]

unused devices: <none>

Notice it was automatically mounted under /dev/md127 for me.

Ok then:

[root@localhost Desktop]# mdadm -A -R /dev/md9 /dev/sdb2 
mdadm: /dev/sdb2 is busy - skipping

[root@localhost Desktop]# mdadm --manage --stop /dev/md/NAS\:0 
mdadm: stopped /dev/md/NAS:0

[root@localhost Desktop]# mdadm -A -R /dev/md9 /dev/sdb2
mdadm: /dev/md9 has been started with 1 drive (out of 2).

[root@localhost Desktop]# mount /dev/md9 /mnt/

That did it for me.

If in doubt, DD the drive to make a full copy and use CentOS or other Linux Live CD.