TMPDIR variable and related issues

Dave Moore dtmoore at
Fri Mar 2 03:51:42 GMT 2001


    After reading the documentation and talking to some of the linux
'gurus' around here, I thought the following setup would work well for
optimizing I/O speed in MOLPRO.

1) Have MOLPRO installed on large (60.0 GB) IDE disk .. users accounts
are located here, so results of calculations will be stored here
2) Set smaller (10.0 GB) very fast 10000 RPM SCSI on fast controller up
as scratch space using TMPDIR variable as specified in INSTALL file.
3) Set another identical SCSI drive up as TMPDIR4.

The SCSI drives are not used for anything else; i.e. the linux-system
and swap-space are on the IDE disk.

However, after I got all of this set up, my calculations run ~2.5 time
SLOWER than if I just put the whole mess (including linux and swap) on
one of the SCSI's, and 5 times SLOWER than when I set the second SCSI up
as TMPDIR4 with everything else on the other SCSI.  I would appreciate
any insights or helpful suggestions the community can offer as to what
(if anything) is wrong with my IDE setup, and how I can improve it.
Thanks in advance. .. by the way .. the timing I am quoting is only for
the integral and swap calculations for a single point calculation of
reasonable size (MOLPRO reports the "disk usage" as 789.7 MB).

Dave Moore
Chemistry Dept.
University of North Carolina at Chapel Hill

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