I built a RAID setup with three drives, two 1.5 TB (sdb and sdd) and one 3TB (sdc). My approach is to combine the two 1.5 TB drives into a RAID0 drive (md3), and create a RAID1 mirror (md2) with the 3TB drive (sdc) and the RAID0 array (md3). This all works.

**The problem**: whenever I reboot the computer, the RAID1 array (md2) only sees one active drive (sdc), even though the RAID0 array (md2) correctly starts up. I have to manually re-add the md2 array each time. What's going on? Is there someway to make the system assemble md3 before it assembles md2?

I already had the md2 drive with sdc. Generally speaking, I've run the commands (approximately):

```
mdadm --create --verbose /dev/md3 --level=stripe --raid-devices=2 /dev/sdb /dev/sdd
mdadm /dev/md2 --add /dev/md3
mdadm --detail --scan >> /etc/mdadm/mdadm.conf

```

I also added "DEVICE partitions containers /dev/md3" to the mdadm.conf file. This is all on Debian 6.0.8.

More information: After rebooting, /proc/mdstat reads (edited out the md0 and md1 info):

```
Personalities : [raid0] [raid1]

md3 : active raid0 sdb[0] sdd[1]
      2930274304 blocks super 1.2 512k chunks

md2 : active raid1 sdc[4]
      1415577600 blocks super 1.2 [2/1] [U_]

unused devices: <none>

```

It seems that md3 (the RAID1 array) has forgotten about md2.

There is also something fishy during startup.

```
dmesg | grep -i 'md2\|md3\|raid'
[    2.537001] md: raid0 personality registered for level 0
[    2.539298] md: raid1 personality registered for level 1
[    2.620402] md: md2 stopped.
[    2.623636] raid1: raid set md2 active with 1 out of 2 mirrors
[    2.623655] md2: detected capacity change from 0 to 1449551462400
[    2.625028]  md2: unknown partition table
[    2.914801] md: md3 stopped.
[    2.919365] raid0: looking at sdb
[    2.919368] raid0:   comparing sdb(2930274304)
[    2.919370] raid0:   END
[    2.919371] raid0:   ==> UNIQUE
[    2.919372] raid0: 1 zones
[    2.919373] raid0: looking at sdd
[    2.919374] raid0:   comparing sdd(2930274304)
[    2.919376] raid0:   EQUAL
[    2.919377] raid0: FINAL 1 zones
[    2.919380] raid0: done.
[    2.919381] raid0 : md_size is 5860548608 sectors.
[    2.919382] ******* md3 configuration *********
[    2.919397] md3: detected capacity change from 0 to 3000600887296
[    2.921296]  md3: unknown partition table
[    3.244104] raid1: raid set md1 active with 2 out of 2 mirrors
[    3.468709] raid1: raid set md0 active with 2 out of 2 mirrors

```