Rpi can't see external hard drive

Question

I got stacked. I have a Raspberry Pi 2 Model B with OSMC installed on it. I want to connect an external drive (Seagate Backup Plus 1TB) to it.

I connected it through a usb hub and there is an additional power source connected to RPi. But my RPi can't see the hard drive.

If I type sudo fdisk -l I get:

Device         Boot  Start     End Sectors  Size Id Type
/dev/mmcblk0p1        2048  499711  497664  243M  c W95 FAT32 (LBA)
/dev/mmcblk0p2      501760 3854335 3352576  1.6G 83 Linux 

As you can see there is no Seagate hard drive.

What am I supposed to do?

dmesg:

[ 3720.753243] usb 1-1.4.3: new full-speed USB device number 12 using dwc_otg
[ 3720.859765] usb 1-1.4.3: not running at top speed; connect to a high speed hub
[ 3720.869524] usb 1-1.4.3: New USB device found, idVendor=0bc2, idProduct=ab21
[ 3720.869558] usb 1-1.4.3: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[ 3720.869576] usb 1-1.4.3: Product: BUP Slim BK
[ 3720.869591] usb 1-1.4.3: Manufacturer: Seagate
[ 3720.869607] usb 1-1.4.3: SerialNumber: NA7805B4
[ 3720.871294] usb-storage 1-1.4.3:1.0: USB Mass Storage device detected
[ 3720.873274] usb-storage 1-1.4.3:1.0: Quirks match for vid 0bc2 pid ab21: 2000000
[ 3720.881189] scsi host5: usb-storage 1-1.4.3:1.0
[ 3721.886536] scsi 5:0:0:0: Direct-Access     Seagate  BUP Slim BK      0143 PQ: 0 ANSI: 6
[ 3721.888811] sd 5:0:0:0: Attached scsi generic sg0 type 0
[ 3721.896262] sd 5:0:0:0: [sda] Spinning up disk...
[ 3727.383243] ....................
[ 3747.558453] usb 1-1.4.3: USB disconnect, device number 12

Answer 1

Based on your dmesg output, it looks like the hard drive isn't getting enough power. It's does the connection phase, and then starts the spin up process. Since this is the most energy intensive task, it makes sense that it would be the point at which the connection fails.

I would suggest switching to a powered USB hub.

Edit:

Based on your comments:

the drive doesn't work with any other computer

and

USB hub is powered

we can reasonably surmise that the drive has a mechanical issue, and that this isn't a problem with the RPi at all.

Edit 2:

Based on a clarifying comment:

If I connect the hard drive through usb-hub to other computers, it doesn't work, but if I connect it without hub, it works.

We're back to the power issue. Your eHDD will require a certain amount of power, just like the RPi does. The back of the drive should list its requirements. Check what the powered hub supports, and what the power supply is giving the hub.