A quick entry to remember a problem which I found creating a new RAID array on my Debian box.
1. This is not a problem is just a reminder: when you create a partition in a hard drive with a GPT label you need to setup as partition type 29 (Linux RAID) instead of partition type fd (Linux RAID) in drive with DOS labels.
2. Problem creating RAID array:
# mdadm --create /dev/md0 --level=mirror --raid-devices=2 /dev/sd[a-b]1 mdadm: Note: this array has metadata at the start and may not be suitable as a boot device. If you plan to store '/boot' on this device please ensure that your boot-loader understands md/v1.x metadata, or use --metadata=0.90 mdadm: super1.x cannot open /dev/sdb1: Device or resource busy mdadm: /dev/sdb1 is not suitable for this array. mdadm: create aborted
After checking with lsof and mount commands that partition is not been used by any process in the system it’s needed to be sure that those partitions are not being used in other RAID array:
# mdadm --detail /dev/md0 /dev/md0: Version : 1.2 Raid Level : raid0 Total Devices : 1 Persistence : Superblock is persistent State : inactive Working Devices : 1 Number Major Minor RaidDevice - 8 17 - /dev/sdb1
So let’s to release that partition removing the old array:
# mdadm -vS /dev/md0 mdadm: stopped /dev/md0 # mdadm -vr /dev/md0
Now you can create successfully the new array.
The greatest teacher, failure is.
— Yoda. The Last Jedi