[Bosse_B]

NTFS support in Linux is rather sketchy...
It might be a driver issue that prevents the RPi from writing stuff when it is a NTFS partition rather than a native ext3 or ext4 or even VFAT.

Concerning the power supply
it seems like you are balancing on the border here...
Please note that there are 3 different items to look out for:
1) The setting in config.txt - this is OK as you report.

2) The PSU must be capable of 2A+ if you want to add peripherals to the Pi powered via USB. Probably also OK.

3) (Most overlooked): The micro-USB cable between the PSU and Pi.
It MUST be as short as ever possible and also be using thick wires inside for the power feed!
I think that cables delivered with known brand power supplies expressly designed for charging tablets (as opposed to phones) are a better deal than anybrand types.

Concerning the cable length it is much better to run a mains extension cord to the PSU and place it close to the Pi and then hook it up to the Pi with a USB cable only say 30 cm or so long than doing the opposite with a long USB cable.

When I first started using RPi units I got bit by this problem, which I did not realize until I actually measured the voltage on the Pi itself and found the 5V to be only about 4.5V.
In the other end (the PSU) I measured 5.1V so the PSU itself was good but not the cable. Ethernet would not work reliably with this voltage.
I ended up by cutting the cable connectors off (with some 5 cm cable), then soldering in thicker wires to the red and black wires in the cable (the other wires are not used).
After I connected the PSU with this modified cable all was good and dandy!

[trogggy]

Also, the hdd works fine including writing new files when the hdd is formatted to FAT32. after writing files worked on FAT32 i formatted it back to NTFS - and again - i can read the files, but not write them.

Might have been an idea to mention that before?
So the problem's 'Can't write to NTFS hdd', not 'can't write to hdd.'
Have you tried an NTFS flash drive? Does that work?
Do you have a different drive you can test with?

Anyway I've tried to reproduce and I can't.
Fresh install of openelec on a pi (v1 though), tested with 4 different NTFS drives, all worked read / write.
It also works on my openelec revo.
So unless there's something completely different happening with the pi 2 it looks like a problem with your openelec or a problem with your drive.
If it were me I would try writing openelec to a new sd card, try the same drive, see if it works...
if not...
run checkdisk on the drive in windows...
try formatting on a different machine / with different software...
perform a low-level format on the drive...
buy a new drive.

Edit: if you just want to put >4GB files on the drive you could try formatting it to exFAT - that will work with windows and it's way quicker than NTFS on the pi.

[6quin3]

I'm sorry for the confusion but I posted that it works on fat32 as soon as i found out that it does. I didnt think before that it could be a problem with the filesystem.

I tried reformatting an usb stick from fat32 to ntfs - and when i plugged it to the pi i was able to read, but not create or delete files. I can now confirm that it is a problem with the filesystem.

I formatted one partition of my hdd to exFAT like you suggested. It works! I can write on my hdd via network. Though I have no clue why it doesnt work with NTFS it doesnt seem to matter. I am now able to use my hdd formatted to exFAT both on my pi and on windows which makes it the best solution.

Thank you all for your help and @troggy thank you very much for the solution.

[trogggy]

Ah, probably me then - somehow I got the impression that that wasn't new info.
Anyway I'm still at a loss to understand why it doesn't work - if Gearbest ever send me the pi2 I ordered from them I'll try an ntfs drive with it.
Glad you've got a solution that works - it's arguably better to use exFAT anyway.