[Lustre-devel] Queries regarding LDLM_ENQUEUE

[Paul Nowoczynski <pauln@psc.edu>]

have a look at this, it explains the type of problem networks have in 
dealing with these communication patterns. 
http://www.pdl.cmu.edu/Incast/

and yes, a proxy is a workable solution, and probably the most well 
rounded.  The disadvantages  is that it would presumably require more 
engineering to deploy.
p



bzzz.tomas at gmail.com wrote:
> On 10/20/10 9:11 PM, Paul Nowoczynski wrote:
>   
>> I could be wrong but my guess is that the network congestion caused by
>> this communication pattern is a more serious problem. The mds should be
>> able to easily service lookup rpc's since only the first few necessitate
>> a read I/O from the disk.
>>     
>
> but then the network should be able to deal with storm of
> <max RPC in-flight> * <# clients> to read/write data?
>
> or it's a specific switch being the bottleneck to specific node?
>
> because if it isn't network, but MDS being a real bottleneck,
> then proxy might be a solution like Eric said above. not sure
> is this important in your case, but this would allow to use
> existing apps.
>
> of course, distribution tree for a handle may scale better.
>
> thanks, z
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