RAID 0 partitioning for Linux installation

Question

I have recently bought ASUS Zenbook UX32VD with 128Gb SSD, which seems to be RAID-0 made from two 64Gb SSD drives. It has Windows 8 preinstalled.

I want to install Arch Linux on it, while keeping Windows 8. But I am having problems with partitioning this RAID-0. I was able to shrink Windows 8 partition from Windows disk management and got about 30Gb of unallocated space, but when I launch Linux from LiveUSB, I can't understand how to proceed with partitioning.

I can see /dev/sda and /dev/sdb, which seem to be corresponding to SSD drives in my RAID-0. blkid gives me the following for these drives:

/dev/sdb: TYPE="isw_raid_member" 
/dev/sda: TYPE="isw_raid_member" 

But when I launch gparted on Kali Linux booted from Live USB, it gives me the following alert windows:

• First, "Libparted Bug Found!: Invalid argument during seek for read on /dev/sda" with "Retry", "Ignore", "Cancel" buttons.
• I press "Ignore" and get "Libparted Bug Found!: The backup GPT table is corrupt, but the primary appears OK, so that will be used" with "OK" and "Cancel" buttons.
• I press "OK" and get "Libparted Bug Found!: Assertion (last_usable <= disk->dev->length) at ../../../libparted/labels/gpt.c:723 in function _parse_header() failed." with "No" button.
• I press "No" and gparted exits.

So my question is: how can I make a new partition on this configuration for Linux to install there while keeping Windows?

---

Additional info:

gdisk on /dev/sda gives me

Warning! Disk size is smaller than the main header indicates! Loading
secondary header from the last sector of the disk! You should use 'v' to
verify disk integrity, and perhaps options on the experts' menu to repair
the disk.
Caution: invalid backup GPT header, but valid main header; regenerating
backup header from main header.

Warning! One or more CRCs don't match. You should repair the disk!

Partition table scan:
  MBR: protective
  BSD: not present
  APM: not present
  GPT: damaged

****************************************************************************
Caution: Found protective or hybrid MBR and corrupt GPT. Using GPT, but disk
verification and recovery are STRONGLY recommended.
****************************************************************************

Command (? for help): p
Disk /dev/sda: 125045424 sectors, 59.6 GiB
Logical sector size: 512 bytes
Disk identifier (GUID): 72D98FD5-AFA6-4935-8DF5-B325A9C2B722
Partition table holds up to 128 entries
First usable sector is 34, last usable sector is 230686686
Partitions will be aligned on 2048-sector boundaries
Total free space is 62918589 sectors (30.0 GiB)

Number  Start (sector)    End (sector)  Size       Code  Name
   1            2048          616447   300.0 MiB   EF00  EFI system partition
   2          616448         2459647   900.0 MiB   2700  Basic data partition
   3         2459648         2721791   128.0 MiB   0C01  Microsoft reserved part
   4         2721792       125087743   58.3 GiB    0700  Basic data partition
   5       188002304       188721151   351.0 MiB   2700  
   6       188721152       230684671   20.0 GiB    2700  Basic data partition

gdisk on /dev/sdb gives me

Partition table scan:
  MBR: not present
  BSD: not present
  APM: not present
  GPT: not present

Creating new GPT entries.

Command (? for help): p
Disk /dev/sdb: 125045424 sectors, 59.6 GiB
Logical sector size: 512 bytes
Disk identifier (GUID): 8BA050D6-16B3-418E-BAAE-7E2916A15267
Partition table holds up to 128 entries
First usable sector is 34, last usable sector is 125045390
Partitions will be aligned on 2048-sector boundaries
Total free space is 125045357 sectors (59.6 GiB)

Number  Start (sector)    End (sector)  Size       Code  Name

Answer 1

What you're asking is basically the same as this question. I'll add, though, that you should use gdisk, parted, or other partitioning tools on the RAID device in Linux, not on the underlying disk devices (/dev/sda and /dev/sdb).