PC GAMESS/Firefly-related discussion club

Learn how to ask questions correctly

Alex Granovsky
gran@classic.chem.msu.su

this problem is important only for calculations that produce
large amount of data stored in temporary disk files which cannot
be efficiently cached by OS due to their overall size.

E.g., conventional SCF for large systems is the excellent sample.  

I'd recommend you to use direct methods as much as possible.
However, there are calculation types which use lots of disk
even when running in direct (actually semidirect) mode.

In particular, they include large scale MP2 energy,
MP2 gradient, MP3/MP4, GUGA CI/MCSCF with large active
spaces, as well as several other types of calculations.

In your particular case, I'd suggest you jut to run six
PC GAMESS/Firefly processes in parallel, each using its own HDD.
The difference between runs using eight or six cores would
not be any case dramatic. Running only six processes in parallel
you will be able to assign a separate HDD to each process,
thus avoiding huge I/O delays caused by disk mechanics,
and prolonging your disk's lifetime.

You can assign working directories either manually
(using old style syntax), or by mounting HDDs using
mountpoints names which are consistent with Firefly's
-t switch behavior. E.g, you would mount your disks at
c:\scratch\ff.0
c:\scratch\ff.1
c:\scratch\ff.2
c:\scratch\ff.3
...
etc...

and then use -t c:\scratch\ff command line option.

Linux users can just create the appropriate symbolic link.

Regards,
Alex Granovsky





 




On Fri Dec 19 '08 11:50am, Vyacheslav wrote
-------------------------------------------
>Hi,
>I am novice at QM, please, help me.
>1) I have 2xCPU Quad Core Xeon, i.e. 8 cores, but 6 HDDs only. How to use these disks to achieve the optimal performance of Firefly in parallel mode with OS Server 2008?