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LASSP: Condensed-Matter Physics Status Report - 4th Quarter
 | Accomplishments |
| Next Quarter Plans |
| Contacts |
| Equipment Utilization |
| Feedback and Problems
Accomplishments
The Linux machines have taken over as the theory group's computational workhorse.
Large-scale computations on exotic boron crystals, electronic structure calculations of
metal-glass interfaces via electronic density functional theory, charge exchange near
surfaces, and Barkhausen noise in magnetic hysteresis are currently underway within the
group. The NT machines are becoming increasingly popular due to the Visual C++ programming
environment, and many of the younger sophisticated graduate students use them extensively.
Next Quarter Plans
In the next quarter, we expect to re-install the operating systems of the NT machines,
making them more stable and uniform.
Contacts
James P. Sethna, Professor, Department of Physics
Ralph B. Robinson, Programmer Analyst, Physics Department
Equipment Utilization
The two new Xeon machines are particularly popular, due both to their speed and (more
importantly) due to the relatively large memories. We have not yet replaced our Silicon
Graphics Onyx supercomputer with the Xeon machine, largely because of the latter's larger
memory.
The configuration of the network and the other machines remain unchanged.
Feedback
We were discouraged to find that the planned upgrades of our existing machines to
current processors was considered infeasible. We expect to shift the current machines to
faculty offices when the new machines arrive in Q2 or Q3, and newer processors would
generate more excitement...
Last modified on: 07/07/98
LASSP: Condensed-Matter Physics Status Report - 2nd Quarter
 | Accomplishments |
| Next Quarter Plans |
| Contacts |
| Equipment Utilization |
| Feedback and Problems
Accomplishments
In conjunction with the Cornell Center for Materials Research branch
of the project, our machines are set up and running, both NT and Linux,
using the AFS file system.
We have had performance difficulties with Developers Studio (our main
tool for research computation) under NT, and many of the sophisticated
NT programmers have remained using the physics service courses facility
for their research work (see below under Equipment Utilization and
Feedback). The NT machines have seen some substantial use in running
working programs and in more routine applications. We are working hard
on improving the performance.
The Linux machines are seeing heavy usage in studies of electromigration
and void dynamics, in electronic structure calculations, in studying
quantum eigenstates of chaotic systems, and in many other simulations.
Next Quarter Plans
Within the next quarter, we expect to see significant scientific
results growing out of the use of this new equipment, which will be
reported here. We also anticipate a prompt resolution of the performance
problems under NT AFS.
Contacts
James P. Sethna, Professor, Department of Physics
Ralph B. Robinson, Programmer Analyst, Physics Department
Equipment Utilization
Five of the machines delivered at the beginning of this quarter are
running dual-processor Linux in the main research facility; five are
running NT over AFS (Andrew File System) there. One, running NT Server,
is in use by a new faculty member in LASSP. All are networked via fast
Ethernet via the 24-port Intel 510T switch, which also is connected to
our AFS server.
AFS provides significant advantages over NFS or other shared file
systems in administration, reliability, security, and network bandwidth.
Mike Heisler, the head of our CCMR computing facility and the person in
charge of the CCMR portion of the Intel project, provides the following
list of crucial features:
 | Administration
| Ease and transparency of moving volumes: Can move software or
home files between disks or servers on-the-fly without
disruptions and without users even knowing it. |
| Replication: Performance improvement (least busy server
responds), subnets across campus have "local" copy. |
| Client specific access features: Binaries are client OS
specific without user or system intervention i.e. typing cc on
Linux or SGI gets you the appropriate compiler. |
|
| Reliability
| Backup facility: |
| "Yesterday" - nightly copy of your files for
undelete |
| Replication - Redundancy of server info and files. |
|
| Security
| Kerberos authentication - secure and robust |
| ACL (Access Control Lists) - Well beyond normal unix
permissions. Similar to NT security
controls |
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| Network Bandwidth
| Local Cache keeps frequently used files on the client. (this
is a 2-edged sword!) |
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We have extensive experience with it under various flavors of Unix. We
are having significant difficulty configuring our NT machines under AFS.
Microsoft software, particularly the help files, expects to write
temporary files into system file directories. This seems bizarre to us.
Naturally, AFS by default refuses to allow ordinary users to write in
system directories. We don't understand how this is compatible with NT's
security either.
There is a serious performance hit in running Developer's Studio on a
remote server running AFS, that has discouraged users from shifting from
the Intel teaching facility which they used last semester. We believe
this is in part due to the large number of small system files that
Windows incorporates as part of its user interface: a small lag time for
each file translates into an enormous slowdown. We suspect that each
file may be stored both in AFS cache and in NT cache; this is a flaw in
the implementation of AFS, which Transarc should be encouraged to fix
(see below). Our AFS server performance may also be part of the problem.
Unfortunately, Transarc does not support AFS server on either Linux or
NT: we suggest that this support might be of some importance to Intel
(see feedback below). Our current plan is to shift to installing much of
the software locally on each machine, which is a significant investment
in disk space and a support headache.
Feedback
Currently we need to use a non-Intel machine as our file server, as
Transarc does not support AFS servers under either Linux or NT. We
strongly suggest supporting and encouraging Transarc to port their AFS
server to Linux, and to improve their NT implementation of AFS client.
AFS is the network file system of choice in the scientific and
computational community, and runs at the various supercomputer centers:
implemented properly, it could be a significant value for Intel's
customers.
We still await a good method to run remote jobs under Windows NT.
Last modified on: 07/07/98
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LASSP: Condensed-Matter Physics Status Report - 1st Quarter
Since the bulk of our equipment is yet to arrive, our focus has been on
getting the software and hardware configurations set up properly so that the new
machines will become immediately useful. In conjunction with the Cornell
Center for Materials Research branch of the project, our machines now run on
the same AFS server which runs our AIX and Linux systems.
Scientifically, the two machines in publicly available areas have seen heavy
usage in electronic structure calculations, in studying quantum eigenstates of
chaotic systems, and in many other simulations: they have whetted our appetite
for the substantial influx to come! The one machine running Windows NT has been
particularly popular with faculty who need access to Microsoft Office
applications to interact with grant agencies.
In about one week, we expect a substantial influx of new machines. The
existing machines will be removed from the computer rooms on the fifth and sixth
floors, keeping only two RS6000's with large memories. The new machines will be
installed, simultaneously shifting to fast switched Ethernet.
Over the past semester, we have been running a graduate physics course on Simulations
under NT, running in the physics service courses
facility. This course, which has been extremely successful and popular, has
brought a large corps of talented graduate students and post-docs up to the
leading edge of current simulations research, while introducing them to C++ and
MFC GUI interfaces. We expect great things to happen in LASSP over the summer
when these students come in to take over the computer room.
James P. Sethna, Professor,
Department of Physics
Ralph B. Robinson, Programmer
Analyst, Physics Department
Three dual-processor Pentium Pro servers have arrived so far. One is being
used as a Linux compute server; one is running Windows NT Server and is running
NTAFS: both are heavily in demand both for large-scale computations and for fast
response. The third machine is being used by Barry Robinson for system
development. All are networked with fast Ethernet via the 24-port Intel 510T
switch, which also is connected to our AFS server. We currently are not using
the eight-port Intel switch (see below).
| We still await a good method to run remote jobs under Windows NT. This
will become crucial in the next quarter, when the bulk of the machines
arrive. It may well be the primary bottleneck to shifting away from Linux. |
| Linux runs wonderfully well on this platform: Unix workstation vendors
beware! |
| These three early machines came before the shift to Dell as the primary
supplier; they had serious idiosyncrasies. When we installed third-party PCI
video cards, the machines refused to boot. Installing a PCI ethernet card
refused to work on the primary PCI bus, but would work on the second PCI
bus. We aren't focusing on our experiences with these machines, because we
expect that feedback about the mainstream supplier will be more useful both
for Intel and for our compatriots at other institutions. |
| The fast Intel 510T Ethernet switches have worked extremely well: we had
only relatively minor problems with the installation. |
| The earlier eight-port switch had an interesting feature: if set up for
remote administration via Telnet, outsiders can log on with a backdoor
password which could not be disabled. We initially disabled Telnet, but are
currently running with the 24-port 510T switch which does not suffer from
this security hole. |
| We learned a lot from setting up the Physics
Service Courses facility: see that report for our major and minor
experiences with cloning our workstation configurations with Drive Image
Professional, and the search for XY plotting routines. |
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