I have a vendor preformatted hard disk (Verbatim Store'n'Save USB 3.0 4TB). When connecting to my CentOS 6 server I can see 2 block devices /dev/sdd and /dev/sde with appropriate partitions, each of them about 2TB size. dmesg gives:

usb 4-4: new SuperSpeed USB device number 3 using xhci_hcd
usb 4-4: LPM exit latency is zeroed, disabling LPM.
usb 4-4: New USB device found, idVendor=18a5, idProduct=0400
usb 4-4: New USB device strings: Mfr=1, Product=2, SerialNumber=3
usb 4-4: Product: USB 3.0 Desktop HD
usb 4-4: Manufacturer: Verbatim
usb 4-4: SerialNumber: 30624C151155
usb 4-4: configuration #1 chosen from 1 choice
scsi7 : SCSI emulation for USB Mass Storage devices
usb-storage: device found at 3
usb-storage: waiting for device to settle before scanning
usb-storage: device scan complete
scsi 7:0:0:0: Direct-Access     TOSHIBA  MD04ACA400       FP2A PQ: 0 ANSI: 6
scsi 7:0:0:1: Direct-Access     TOSHIBA  MD04ACA400       FP2A PQ: 0 ANSI: 6
sd 7:0:0:0: Attached scsi generic sg4 type 0
sd 7:0:0:1: Attached scsi generic sg5 type 0
sd 7:0:0:0: [sdd] 4294965248 512-byte logical blocks: (2.19 TB/1.99 TiB)
sd 7:0:0:0: [sdd] Write Protect is off
sd 7:0:0:0: [sdd] Mode Sense: 1f 00 00 08
sd 7:0:0:0: [sdd] Assuming drive cache: write through
sd 7:0:0:1: [sde] 3519071920 512-byte logical blocks: (1.80 TB/1.63 TiB)
sd 7:0:0:1: [sde] Write Protect is off
sd 7:0:0:1: [sde] Mode Sense: 1f 00 00 08

fdisk gives:

fdisk -l /dev/sdd

Disk /dev/sdd: 2199.0 GB, 2199022206976 bytes
255 heads, 63 sectors/track, 267349 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x1428089d

   Device Boot      Start         End      Blocks   Id  System
/dev/sdd1               1      267350  2147480576    c  W95 FAT32 (LBA)

I want to have only one device with 4TB size. I tried to use parted to set the disk-label-typ to GPT but without success.