When I fired up my Readynas nv+ v2, I didnt have a copy of the RAIDar admin tool running, so it defaulted to creating an xraid2 volume. This was fine, apart from after the 2x 1TB disks were initialised, I couldnt add the 2 500GB disks from my old box. This is my account of how I (hopefully) create a 2nd volume
I already had root ssh access enabled, so with a quick scout around the file system, I could see that lvm and md were used in creating some of the raid arrays.
So to see what was on each disk, I used fdisk -l
fdisk -l /dev/sda
WARNING: GPT (GUID Partition Table) detected on '/dev/sda'! The util fdisk doesn't support GPT. Use GNU Parted.
Disk /dev/sda: 1000.2 GB, 1000204886016 bytes
256 heads, 63 sectors/track, 121126 cylinders
Units = cylinders of 16128 * 512 = 8257536 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000
Device Boot Start End Blocks Id System
/dev/sda1 1 121127 976762583+ ee GPT
So this shows that on the first sata disk, there is a 1000 GB disk, sdb was also the same, with sdc and sdd both showing as 500 GB disks
Now that I knew which disks I wanted to meddle with, I could start to prepare the array. I found some instructions on www.cyberciti.biz which I approximately followed.
mdadm --create /dev/md3 --level=1 --raid-devices=2 /dev/sdc1 /dev/sdd1
mkfs.ext3 /dev/md3
ln -s /dev/md3 /dev/d
mkdir /d mount /dev/d /d
I'm yet to reboot and test that the disk is found at next boot, but it is usable. The nas admin website doesnt allow me to share it and make use of it that way yet. But looking at what else is going on, it appears that the /c volume uses lvm, so I may try creating an lvm partition on the md partition, and see how the nas copes