Have I actually created a RAID 1 device?

I decided to reuse two ext4 HDDs from my Qnap server in my Omnia RAID.

As such, I simply mounted the UUID, rather than use mdadm to create the /dev/md0 device as suggested in this thread:

When I add content (a large file, for example) to the drive, the capacity of /dev/sda3 and /dev/sdb3 appear to change correspondingly.

The questions:

  • have I actually created a RAID 1 device?
  • should I be using mdadm?

Supporting information:

# lsblk
sda            8:0    0   1.8T  0 disk 
|-sda1         8:1    0 517.7M  0 part /tmp/run/mountd/sda1
|-sda2         8:2    0 517.7M  0 part 
|-sda3         8:3    0   1.8T  0 part /tmp/run/mountd/sda3
`-sda4         8:4    0 486.3M  0 part /tmp/run/mountd/sda4
sdb            8:16   0   1.8T  0 disk 
|-sdb1         8:17   0 517.7M  0 part /tmp/run/mountd/sdb1
|-sdb2         8:18   0 517.7M  0 part 
|-sdb3         8:19   0   1.8T  0 part /tmp/run/mountd/sdb3
`-sdb4         8:20   0 486.3M  0 part /tmp/run/mountd/sdb4
mtdblock0     31:0    0     1M  0 disk 
mtdblock1     31:1    0     7M  0 disk 
mmcblk0      179:0    0   7.3G  0 disk 
`-mmcblk0p1  179:1    0   7.3G  0 part /
mmcblk0boot0 179:8    0     4M  1 disk 
mmcblk0boot1 179:16   0     4M  1 disk 
mmcblk0rpmb  179:24   0     4M  0 disk 


# df -h
Filesystem                Size      Used Available Use% Mounted on
/dev/mmcblk0p1            7.3G      1.6G      5.7G  22% /
tmpfs                   503.6M     15.5M    488.1M   3% /tmp
tmpfs                   512.0K      4.0K    508.0K   1% /dev
/dev/sda3                 1.8T    529.0G      1.3T  29% /mnt/raid
/dev/sdb3                 1.8T    529.0G      1.3T  29% /mnt/raid
/dev/sdb4               355.0M    351.7M      3.3M  99% /tmp/run/mountd/sdb4
/dev/sdb3                 1.8T    529.0G      1.3T  29% /tmp/run/mountd/sdb3
/dev/sdb1               493.5M    111.1M    382.4M  23% /tmp/run/mountd/sdb1
/dev/sda4               355.0M    351.7M      3.3M  99% /tmp/run/mountd/sda4
/dev/sda3                 1.8T    927.4G    904.2G  51% /tmp/run/mountd/sda3
/dev/sda1               493.5M    111.1M    382.4M  23% /tmp/run/mountd/sda1

try btrfs filesystem df <mount>
in your case: btrfs fi df /mnt/raid

The answer seems to be ‘no’:

# btrfs fi df /mnt/raid
ERROR: not a btrfs filesystem: /mnt/raid

my bad, sorry… I just realized you made it ext4
(which is weird since you have followed a howto in which they used btrfs)

(which is weird since you have followed a howto in which they used btrfs)

Not weird. I have two Turris (Turrises?, Turrii?): mine and a friends that I’m (trying to) configure.

Mine has two ext4 drives that I pulled from a QNAP. My friend’s is btrfs (which I followed the howto).

I still don’t think that mine is actually a RAID (because I didn’t use mdadm to create it), even though it seems to be acting like one (inexplicably).