UI freezes while copying large file via NFS

[Konstantin Svist]

  On 08/09/2010 12:36 PM, Patrick O'Callaghan wrote:
> I've been copying some large (several GB) files from my local system to
> a NAS server on my LAN, using NFS.
>
> The local files are on an external USB drive (Iomega 500GB unit) on a
> USB 2 port. The NAS server is also Iomega, an ix-200. The network switch
> is a Belkin Wireless G with 100Mbps Ethernet ports (I'm not using Wifi
> for this). I'm not using jumbo frames or anything fancy, in fact I don't
> think the Belkin supports them. The system is an Intel Core 2 Duo mobo
> with 4GB RAM running F13 fully updated.
>
> I'm using KDE 4.4.5. When I do one of these copies (using cp from a
> terminal), my entire system becomes unresponsive for periods of about 1
> minute, then becomes usable for maybe 10 seconds, freezes again for
> another minute etc. etc. until the copy finishes. "Unresponsive" means
> the mouse cursor won't move, button clicks aren't attended to and I
> can't type in Konsole or in the Evolution mail composer.
>
> Copying the same files to a local SATA disk doesn't cause this
> phenomenon, so it can't just be the external drive. OTOH, I use the same
> NAS for regular rsync-based backups *to the same NFS-mounted NAS* and
> the load is not noticeable.
>
> Any thoughts on this would be welcome.
>
> poc

Usually you see this kind of problem when your HDD is thrashing.

Try running your copy command with ionice:
ionice -c3 <command>

Other things to check:
* run top in a separate window before you run the freezing command -- 
see what it says when it works
* see if tty sessions in Ctrl+Alt+F2..F6 respond any better than the UI