Mirroring a.k.a. RAID 1 - Followup

When connecting my two mirrored drives created with mdadm to another machine (my labtop in this case), this happens:

[ 3006.059308] usb 2-1.1: new high-speed USB device number 3 using ehci_hcd
[ 3006.145807] usb 2-1.1: New USB device found, idVendor=1058, idProduct=1021
[ 3006.145818] usb 2-1.1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[ 3006.145823] usb 2-1.1: Product: Ext HDD 1021
[ 3006.145828] usb 2-1.1: Manufacturer: Western Digital
[ 3006.145832] usb 2-1.1: SerialNumber: 574D43315431373033343231
[ 3006.149589] scsi8 : usb-storage 2-1.1:1.0
[ 3007.154933] scsi 8:0:0:0: Direct-Access WD Ext HDD 1021 2021 PQ: 0 ANSI: 4
[ 3007.157133] sd 8:0:0:0: [sdb] 3907024896 512-byte logical blocks: (2.00 TB/1.81 TiB)
[ 3007.157508] sd 8:0:0:0: Attached scsi generic sg2 type 0
[ 3007.158940] sd 8:0:0:0: [sdb] Write Protect is off
[ 3007.158956] sd 8:0:0:0: [sdb] Mode Sense: 17 00 10 08
[ 3007.160824] sd 8:0:0:0: [sdb] No Caching mode page present
[ 3007.160835] sd 8:0:0:0: [sdb] Assuming drive cache: write through
[ 3007.166300] sd 8:0:0:0: [sdb] No Caching mode page present
[ 3007.166312] sd 8:0:0:0: [sdb] Assuming drive cache: write through
[ 3007.182900] sdb: sdb1
[ 3007.188055] sd 8:0:0:0: [sdb] No Caching mode page present
[ 3007.188067] sd 8:0:0:0: [sdb] Assuming drive cache: write through
[ 3007.188073] sd 8:0:0:0: [sdb] Attached SCSI disk
[ 3007.764265] md: bind
[ 3013.631277] usb 2-1.2: new high-speed USB device number 4 using ehci_hcd
[ 3013.717235] usb 2-1.2: New USB device found, idVendor=1058, idProduct=1021
[ 3013.717246] usb 2-1.2: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[ 3013.717251] usb 2-1.2: Product: Ext HDD 1021
[ 3013.717256] usb 2-1.2: Manufacturer: Western Digital
[ 3013.717261] usb 2-1.2: SerialNumber: 574D43315432313138383334
[ 3013.718543] scsi9 : usb-storage 2-1.2:1.0
[ 3014.722760] scsi 9:0:0:0: Direct-Access WD Ext HDD 1021 2021 PQ: 0 ANSI: 4
[ 3014.724734] sd 9:0:0:0: Attached scsi generic sg3 type 0
[ 3014.725314] sd 9:0:0:0: [sdc] 3907024896 512-byte logical blocks: (2.00 TB/1.81 TiB)
[ 3014.727731] sd 9:0:0:0: [sdc] Write Protect is off
[ 3014.727744] sd 9:0:0:0: [sdc] Mode Sense: 17 00 10 08
[ 3014.729563] sd 9:0:0:0: [sdc] No Caching mode page present
[ 3014.729575] sd 9:0:0:0: [sdc] Assuming drive cache: write through
[ 3014.735276] sd 9:0:0:0: [sdc] No Caching mode page present
[ 3014.735287] sd 9:0:0:0: [sdc] Assuming drive cache: write through
[ 3014.753371] sdc: sdc1
[ 3014.758786] sd 9:0:0:0: [sdc] No Caching mode page present
[ 3014.758796] sd 9:0:0:0: [sdc] Assuming drive cache: write through
[ 3014.758802] sd 9:0:0:0: [sdc] Attached SCSI disk
[ 3015.063908] md: bind
[ 3015.153298] md: raid1 personality registered for level 1
[ 3015.153537] bio: create slab at 1
[ 3015.153667] md/raid1:md127: not clean -- starting background reconstruction
[ 3015.153670] md/raid1:md127: active with 2 out of 2 mirrors
[ 3015.153729] md127: detected capacity change from 0 to 2000261283840
[ 3015.161179] md127: unknown partition table

Turns out, a device is automatically made, called /dev/md127.