I have same NAS but with 3x2TB disks.
It indeed uses small linux partition over all disks, but also creates 4 partitions on each disk and then combines storage partitions into VG/LV.
Code:
/opt/sbin $ fdisk -l
Disk /dev/sda: 2000.3 GB, 2000398934016 bytes
255 heads, 63 sectors/track, 243201 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sda1 1 26 208844+ fd Linux raid autodetect
/dev/sda2 27 156 1044225 fd Linux raid autodetect
/dev/sda3 157 176 160650 fd Linux raid autodetect
/dev/sda4 177 18446744073709527469 18446744073514166281+ fd Linux raid autodetect
Disk /dev/sdb: 2000.3 GB, 2000398934016 bytes
255 heads, 63 sectors/track, 243201 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sdb1 1 26 208844+ fd Linux raid autodetect
/dev/sdb2 27 156 1044225 fd Linux raid autodetect
/dev/sdb3 157 176 160650 fd Linux raid autodetect
/dev/sdb4 177 18446744073709527469 18446744073514166281+ fd Linux raid autodetect
Disk /dev/sdc: 2000.3 GB, 2000398934016 bytes
255 heads, 63 sectors/track, 243201 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Device Boot Start End Blocks Id System
/dev/sdc1 1 26 208844+ fd Linux raid autodetect
/dev/sdc2 27 156 1044225 fd Linux raid autodetect
/dev/sdc3 157 176 160650 fd Linux raid autodetect
/dev/sdc4 177 18446744073709527469 18446744073514166281+ fd Linux raid autodetect
Disk /dev/sdd: 1010 MB, 1010826752 bytes
255 heads, 63 sectors/track, 122 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
...
Code:
/opt/sbin $ mount
/dev/root on /old type cramfs (ro)
proc on /old/proc type proc (rw,nodiratime)
/dev/md0 on / type ext3 (rw,noatime)
proc on /proc type proc (rw,nodiratime)
/proc/bus/usb/ on /proc/bus/usb type usbfs (rw)
/dev/pts on /dev/pts type devpts (rw)
trusteesfs on /trustees type trusteesfs (rw)
/dev/vg0/lv0 on /DataVolume type ext3 (rw,noatime)
/dev/ram0 on /mnt/ram type tmpfs (rw)
Not sure if any of this can be applied to OP-s config since mine is stripped, but this is all i can do.