[Lustre-discuss] high CPU load limits bandwidth?

[Andreas Dilger]

Is this client CPU or server CPU?  If you are using Ethernet it will definitely be CPU hungry and can easily saturate a single core. 

Cheers, Andreas

On 2010-10-20, at 8:41, Michael Kluge <Michael.Kluge at tu-dresden.de> wrote:

> Hi list,
> 
> is it normal, that a 'dd' or an 'IOR' pushing 10MB blocks to a lustre
> file system shows up with a 100% CPU load within 'top'? The reason why I
> am asking this is that I can write from one client to one OST with 500
> MB/s. The CPU load will be at 100% in this case. If I stripe over two
> OSTs (which use different OSS servers and different RAID controllers) I
> will get 500 as well (seeing 2x250 MB/s on the OSTs). The CPU load will
> be at 100% again. 
> 
> A 'dd' on my desktop pushing 10M blocks to the local disk shows 7-10%
> CPU load.
> 
> Are there ways to tune this behavior? Changing max_rpcs_in_flight and
> max_dirty_mb did not help.
> 
> 
> Regards, Michael
> 
> -- 
> 
> Michael Kluge, M.Sc.
> 
> Technische Universität Dresden
> Center for Information Services and
> High Performance Computing (ZIH)
> D-01062 Dresden
> Germany
> 
> Contact:
> Willersbau, Room A 208
> Phone:  (+49) 351 463-34217
> Fax:    (+49) 351 463-37773
> e-mail: michael.kluge at tu-dresden.de
> WWW:    http://www.tu-dresden.de/zih
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