[Beowulf] automount on high ports

Tim Cutts tjrc at sanger.ac.uk
Wed Jul 2 01:19:50 PDT 2008

On 2 Jul 2008, at 8:26 am, Carsten Aulbert wrote:

> OK, we have 1342 nodes which act as servers as well as clients. Every
> node exports a single local directory and all other nodes can mount  
> this.
> What we do now to optimize the available bandwidth and IOs is spread
> millions of files according to a hash algorithm to all nodes (multiple
> copies as well) and then run a few 1000 jobs opening one file from one
> box then one file from the other box and so on. With a short autofs
> timeout that ought to work. Typically it is possible that a single
> process opens about 10-15 files per second, i.e. making 10-15 mounts  
> per
> second. With 4 parallel process per node that's 40-60 mounts/second.
> With a timeout of 5 seconds we should roughly have 200-300 concurrent
> mounts (on average, no idea abut the variance).

Please tell me you're not serious!  The overheads of just performing  
the NFS mounts are going to kill you, never mind all the network  
traffic going all over the place.

Since you've distributed the files to the local disks of the nodes,  
surely the right way to perform this work is to schedule the  
computations so that each node works on the data on its own local  
disk, and doesn't have to talk networked storage at all?  Or don't you  
know in advance which files a particular job is going to need?


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