[GRASS5] GRASS on OpenMOSIX cluster

[Markus Neteler]

On Tue, Jan 14, 2003 at 01:00:33AM +0000, Glynn Clements wrote:
> Markus Neteler wrote:
> 
> > at time I am trying to run GRASS on a 20 node OpenMOSIX cluster.
> > The task to perform is to 'i.smap' 230 aerial images with 3 bands
> > each (later I'll try an improved method).
> > 
> > The main problem is that the various jobs seem to influence
> > each other (especially the current region).
[...]
> For the most part, you can run multiple sessions provided that they
> each operate upon a different mapset. The primary exception is that
> using monitors is problematic (monitor names are per-uid).
> 
> Having multiple sessions using the same mapset is high-risk. It could
> theoretically be done, but to be safe, you would have to analyse the
> behaviour of each command which is intended to be used to ensure that
> no two processes attempt to modify the same file. The most likely
> cause of conflict would be the WIND file.

This was what I was doing (and which didn't work out).
 
Now I have rewritten the job launcher to run every job in a different
mapset (which is easy when you deal with many maps and the same operation
for all maps).

Result: it works well. At end of each job I switch to a common mapset
and copy over the map, then delete the temporary job mapset.

Now we only face NFS problems... when having the target mapset remotely
outside the cluster via NFS, the g.copy command only copies the cell file
properly, while cellhd/, cell_misc, colr and are empty (present, but 0
size). This will be related to openMOSIX. When keeping the target mapset on
local, it works perfectly.

Thanks for the mapset hint,

 Markus