[Beowulf] Computation on the head node

[Vlad Manea]

Thanks Perry,

I would probably go with a separate file server.
I have seen a lot of NAS on the market recently (i.e. Netgear ReadyNAS 
NV+ 4Tb X-RAID)
and I am wandering if they might be a good/bad choice (the price is 
appealing...).
On the other hand I do not want to see all may cluster idle waiting for 
the file server.
The w/r rate transfer for these NAS is ~30-40 MB/sec which probably is a 
modest one.

Do you have any recommendations for the file server? I think I need lots 
of RAM and fast
disks. Since SCSI are expensive, are SATA disks OK? Also, can I take the 
advantage of multiple
LAN ports on the file server? (I see the Dell PowerEdge SC1435 can 
handle 4 NICs for example.)

Since all my machines are from
DELL maybe I can get a discount from them if I would go buying one file 
server.


Thanks,
Vlad

Perry E. Metzger wrote:
> Vlad Manea <vlad at geociencias.unam.mx> writes:
>   
>> I have a question regarding the head node for a small cluster that I
>> would like to build:
>>
>> which are the disadvantages of using the head node as a computation
>> node?  Since I plan to have NFS on it, I guess there will be
>> problems with comunication which probably will slow down the whole
>> cluster, but I am not sure since this is my first attempt to built
>> one...
>>     
>
> As is always the case, "it depends". Your computational load might be
> such that doing computation on the head speeds up the overall
> computation by adding a needed CPU, or might be such that it slows it
> down by robbing the whole cluster of needed file i/o performance. That
> depends enormously on the particular task you're doing. The only real
> way to know is to test it and see what happens.
>
> In general, if you have enough machines, I don't think there is much
> point in doing computation on the head -- it complicates matters and
> if you have enough machines you're only adding a tiny percentage of
> extra CPU -- but if you have a very small cluster and you need the
> extra CPU and your tests say it is fine, then go for it. You'll have
> to test to be sure.
>
> Perry
>   


-- 
*Dr. Vlad Constantin Manea*
*Professor of Geophysics*
Computational Geodynamics Lab. <http://www.geociencias.unam.mx/geodinamica>
Centro de Geociencias,
Campus UNAM, Juriquilla,
Blvd Juriquilla 3001,
Juriquilla, Querétaro, 76230,
México.
phone: +52 55 5623 4104/ext.133
fax: (55) 5623-4129
http://www.geociencias.unam.mx/geodinamica
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