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Why do I need mdadm to create RAID array?
We do so, because it allows us to have an operational RAID array which we can copy our data into and then add the old drive to the array and sync it. These commands instructs mdadm to create a RAID1 array with two drives where one of the drives is missing.
How to replace a failed mirror disk in a RAID array?
Replacing a Failed Mirror Disk in a Software RAID Array (mdadm) 1 Mark the disk as failed. Failed disk will be marked as “ (F)”. 2 Remove the disk by mdadm 3 Replace the disk. Replace the faulty disk with new one. 4 Copy the partition table to the new disk 5 Create mirror 6 Verify
Why do I need initramfs to run mdadm?
It scans the drives, looking for superblocks, and rebuilds all the arrays for you. This is why you need an initramfs when booting off a raid array – because mdadm is a user-space program, if root is on an array then we have a catch-22 – we can’t boot until we have root, and we can’t have root until we’ve booted and can run mdadm.
What happens when you add a new drive to a RAID array?
If you have made it that far, you have a running system with all your data on a degraded RAID array which consists of your new drive. The next step will be to add the old disk to the RAID array. This will delete any existing data on it.
How to set up mdadm on an existing drive?
Before booting the new (degraded) array, we need to copy our data into it. First mount /dev/md/root somewhere, say /mnt/root, and then copy the old data into it. Next you need to update /mnt/root/etc/fstab with the UUIDs of the new partition (which you can get using blkid ). If you have encrypted swap, you should also update /mnt/root/etc/crypttab.
Do you need to set boot flag for mdadm?
You don’t need to bother setting the “raid” flag on your partitions like some people suggest. mdadm will scan all of your partitions regardless of that flag. Likewise, the “boot” flag isn’t needed on any of the partitions. If you haven’t installed mdadm so far, do it: We create a degraded RAID1 array with the new drive.
Where do I find examine option in mdadm?
Use mdadm –examine for more detail. You can get more detailed information by using the -E or –examine options: This information is similar to that displayed when using the -D option with the array device, but focused on the component device’s relationship to the array.
What happens if I have a faulty disk in mdadm?
If a RAID is operated with a spare disk, it will jump in for the disk set to faulty . A rebuild is performed automatically. The disk set to faulty appears in the output of mdadm -D /dev/mdN as faulty spare .
How to add a spare to a RAID 0 array?
Spares cannot be added to non-redundant arrays (RAID 0) because the array will not survive the failure of a drive. To add a spare, simply pass in the array and the new device to the mdadm –add command: