"Buffering..." from USB HDD, but not from netowrk streams

[piontec]

Hi all,
I have a raspi B 256 MB and on a default installation of xbian1.0a5 (no configuration, default parameters accepted) I have the following issue.

I have a fast external HDD attachet via USB to the Pi. When I'm watching SD movies, everything is OK, but in 720p/1080p movies, the movie is every few minutes stopped with the "Buffering..." message from XBMC. The interesting thing is, that network streams, even 1080p, work flawlessly. Is there any way to improve buffering from local drives? Any ideas?

Thanks in advance for any suggestions,

[Koenkk]

Is it a self powered usb hdd? If not, connect it to a powered USB hub.

[piontec]

I doubt it's a power supply problem - the drive shares with the pi a 4A 5V power supply - there should be plenty of current available. Can it be related to the fact, that after running XBMC there is only a limited amount of RAM left for disk buffering? Maybe drive readahead can be tuned?

[Koenkk]

The PI can ony output a X amount of Ma via USB. That X amount is too less to power a USB HDD

[namtih]

What Koenkk is saying is, that you can have a very powerful power adapter connected to the PI. But the USB ports of the PI will only use about 300mA - not more. And those 300mA are often not enough to power a USB drive.

But to test your USB drive and the general performance, you could try to execute this command via SSH:

Terminal

sudo dd if=/dev/sdb1 of=/dev/null bs=32M count=30 iflag=direct

This will create a 900MB test file on your disk.
Please replace "/dev/sdb1" with the indentifier of your USB drive. You should get it via a simple "df".
To give you any number to compare to, here is my result:

Terminal

root@xbian ~ # sudo df
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/sdb1 1953503968 1467509906 485994062 76% /mnt/hdd

root@xbian ~ # sudo dd if=/dev/sdb1 of=/dev/null bs=32M count=30 iflag=direct
30+0 records in
30+0 records out
1006632960 bytes (1.0 GB) copied, 29.0751 s, 34.6 MB/s