The Frailties of mdadm RAID

PSA!!!

As a homelabber I have used several filesystems across many machines. When I first began the simplest was EXT3 and its predecessor EXT4 is still the simplest journaling file system around. After a while I started to look for redundancy via mdadm’s RAID on Linux. From then on I had RAID arrays usually consisting of RAID1 or mirror on most of my systems whether it be on HDDs or SSDs. But only after 10 plus years have I had a reason to take an old unused RAID1 HDD and try to get a file out of the drive, I have found it to be virtually impossible.

There are sites that claim this and that but if you have taken the HDD out of running system or in my case a no longer used server and put in into another system without the paired drive it will not be possible to get to your data.

In a working system you tell the mdadm array that one drive is bad then you could remove it and plug in a new drive and resilver the array. But since in my case I do not have the /etc/mdadm.conf file from the original machine, trying to replicate that file is virtually impossible.

Because of this major error when using mdadm, I will never use it ever again and focus all my energy on zfs.