[Pw_forum] Restarting PWSCF - usability issues

[Francesco Antoniella]

> For machines having a parallel file system (i.e. the sp4 in 
> Cineca, Bologna), the problem is not that serious: all files 
> are in the same place, and the I/O is still very fast (or at 
> least, that is what I understood). Trouble arises only if you 
> want to restart with a different number of processors . 
> 
> For machines without a parallel file system (i.e. the sp3 in
> PMI, Princeton) your *wfc files are scattered on different file 
> systems in different processors (forget using I/O via NFS!).
> Restarting is a mess: you need a copy of all files on all 
> processors, since there is no way to tell which physical
> processor corresponds to which logical one in MPI.
> 
For a PC cluster a good workaround  is to use the openmosix package and
its MFS see-all-the-disks filesystems.
I implemented it in the Attila cluster at L'Aquila university at permits
a quite fast writing via network (better than NFS) and/or accessibility
of the nodes' filesystems in a reasonnably simple way.
Francesco