Ken Cobler wrote:
> H. Sami Sozuer wrote:
>> Hi folks,
>>
>> We have a 20-node cluster that we want to use both as diskless 
>> workstations
>> that connect to a dual Xeon machine as X terminals and as nodes of 
>> our cluster
>> that can run MPI programs. We've installed the ltsp
>> server on a FC5 and tried out a client and there is no problem, the 
>> client
>> gets the gdm login window and can run programs on the server.  However,
>> since we also need to run MPI programs via ssh on the nodes, we need 
>> to have
>> a lot of the standard gcc, glibc, MPI etc on each node. The basic 
>> ltsp filesystem
>> in /opt/ltsp/i386 is very insufficient for this job and simply 
>> copying files from /lib /bin /usr
>> etc onto the clients' / directory seems, ... well just not right. Has 
>> anyone tackled a problem
>> of this sort before? What is the best way to go about installing 
>> these programs on the client
>> filesystem? I can ssh to the diskless clients, no problem there.
>>
>> Thanks for any pointers
>> Sami
>>
>> PS. The reason we don't want to use the hard disks of the clients is 
>> because of the frequent
>> power outages. We can maintain continuous power the server which 
>> houses the hard disks but
>> with 20 machines it's just not feasible.
>>   
> I don't know what MPI is, however, the concept behind LTSP is Terminal 
> Services.  Which means a Linux server can host and run many 
> applications for many terminals.  So, by running the application on 
> the client, you are defeating the purpose of having a terminal 
> server.  Run the application on the server and have the output go to 
> the client terminal.
>
> If you are implying that MPI is a CUI based program which requires you 
> to ssh into the server, then so be it.  If you are looking for better 
> terminal emulation, you can get putty (a popular Windows based 
> terminal emulation program) in source code for Linux to compile for 
> your machine.
>
> Perhaps you can explain MPI and it's features or limitations, and why 
> you wouldn't want it to run on the server only.
>
> Ken Cobler
Ken,

MPI stands for Message Passing Interface and it's the most popular way 
of running
parallel programs on many machines. So MPI itself is not a program but a 
means for
programs running on many nodes of a cluster to communicate and work on a 
single job.
What we have is a student computer lab that gets used for about 10 hours 
a week, and in terms
of CPU usage, the yearly average would probably be less than 0.1 per 
cent! Imagine all those

CPUs just sitting idly for nearly their entire lifetime.
So what we thought would be smart was to have each machine connect to a 
server, LTSP style,
and use the CPU resources of the server, while we wanted to run number 
crunching applications
on the CPUs of each individual node (3GHz P4 Prescott). The server alone 
is just too inadequate for
the number crunching jobs we have. The problem was that the programs 
installed on the client
nodes' filesystem was too inadequate, and it was very difficult to 
install programs on the server
when you chroot /opt/ltsp/i386 and try the configure&&make&&make install 
routine.
But I tried copying the files by hand and it looks like maybe it will be 
possible to get things working
anyhow.

I like ltsp because of the local device support, and NFS swapping and so 
on. Of course it wasn't
designed for using a student computer lab as a HPC cluster, but with the 
current speed of processors
and the prices of GigE switches, I have a feeling there will be more 
people trying to build this
type of "dual use" labs  in the near future.


Sami



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