mdadm upgrade

Even though I spend little of my free time with sysadmin stuff these days, this came up recently. A few years ago I hit an issue about mdadm creating too new metadata that wasn’t handled by the installed kernel, so I remembered to use --metadata 0.90 when creating a new array. Additionally, I preferred using cfdisk for partitioning.

It turns out this caused quite some grief when it came to grub2, I wrote about this earlier — that was about the theory, in a VM. This is about the practice. In practice, gparted turned out to be too risky, and I choose the following approach to repartition the hard drives (so there is enough space for grub2) and upgrade the mdadm metadata.

First, I broke the mirror by removing one leg of the RAID1 array:

Then I created a new array (with a single leg) with the new metadata and formatted it:

Finally I copied over the live system:

The rest was easy: I booted a livecd to do the rsync once again (taking a few minutes only), and once the system was running from the new array, added the leg of the old array to the new one as well — and that’s it.