External USB HDDs used for RAID1 keep changing /dev identifiers.

Greetings.

I'm trying to use a Mediasonic Probox HF2-SU3S2 drive enclosure with Linux software RAID via mdadm. I have installed 4 drives in the enclosure, with two of the drives (2 TB each) I'm trying to configure as RAID1. The enclosure is coected to my system via USB 3.0. Initially I can see the two drives as /dev/sdb and /dev/sdd. When I do the command to create the RAID the enclosure appears to reset (all the panel lights start flashing, and when the enclosure comes back online the drive designations have changed.

Here's a look at what I'm doing:

tom@topcat:~$ lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 698.7G 0 disk
├─sda1 8:1 0 694.9G 0 part /
├─sda2 8:2 0 1K 0 part
└─sda5 8:5 0 3.8G 0 part [SWAP]
sdb 8:16 0 1.8T 0 disk (in the enclosure)
└─sdb1 8:17 0 1.8T 0 part
sdd 8:48 0 1.8T 0 disk (in the enclosure)
└─sdd1 8:49 0 1.8T 0 part
sdf 8:80 0 3.7T 0 disk
└─sdf2 8:82 0 3.7T 0 part /media/M
sdg 8:96 0 931.5G 0 disk
└─sdg1 8:97 0 931.5G 0 part /media/L
sdh 8:112 0 931.5G 0 disk (in the enclosure)
sdj 8:144 0 298.1G 0 disk (in the enclosure)
└─sdj1 8:145 0 298.1G 0 part /media/V
sr0 11:0 1 1024M 0 rom

tom@topcat:~$ sudo mdadm --create --verbose /dev/md0 --level=mirror --raid-devices=2 /dev/sdb1 /dev/sdd1
mdadm: /dev/sdb1 appears to contain an ext2fs file system
size=1953411072K mtime=Wed Dec 31 19:00:00 1969
mdadm: /dev/sdb1 appears to be part of a raid array:
level=raid1 devices=2 ctime=Thu Mar 17 23:04:34 2016
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: /dev/sdd1 appears to contain an ext2fs file system
size=1953411072K mtime=Wed Dec 31 19:00:00 1969
mdadm: /dev/sdd1 appears to be part of a raid array:
level=raid1 devices=2 ctime=Thu Mar 17 23:04:34 2016
mdadm: size set to 1953279808K
Continue creating array? y
mdadm: Defaulting to version 1.2 metadata
mdadm: array /dev/md0 started.

tom@topcat:~$ lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 698.7G 0 disk
├─sda1 8:1 0 694.9G 0 part /
├─sda2 8:2 0 1K 0 part
└─sda5 8:5 0 3.8G 0 part [SWAP]
sdc 8:32 0 1.8T 0 disk
└─sdc1 8:33 0 1.8T 0 part
sde 8:64 0 1.8T 0 disk
└─sde1 8:65 0 1.8T 0 part
sdf 8:80 0 3.7T 0 disk
└─sdf2 8:82 0 3.7T 0 part /media/M
sdg 8:96 0 931.5G 0 disk
└─sdg1 8:97 0 931.5G 0 part /media/L
sdh 8:112 0 931.5G 0 disk
sdi 8:128 0 298.1G 0 disk
└─sdi1 8:129 0 298.1G 0 part
sr0 11:0 1 1024M 0 rom

The drive designations flip between sdb/sdd and sdc/sde. It's consistent. In fact, as you can see, all the drives in the enclosure get new designations.

I'm ruing Ubuntu 14.04 with all the software up-to-date.

tom@topcat:~$ uname -a
Linux topcat 3.16.0-36-generic #48~14.04.1-Ubuntu SMP Wed Apr 15 13:11:28 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux

I tried investigating udev to make the drive designators fixed and persistent, but there is nothing unique that I can see between the 2 identical HDDs.

TIA for any help.