VRANA = Vzporedni Računalnik za Akceleracijo Numeričnih Algoritmov.

VRANA is the name of the bird crow in the Slovenian language. CROW could be expanded as Columns and Rows Of Workstations.

CROW = Columns and Rows Of Workstations.

Ceter for Molecular Modeling (CMM),
National Institute of Chemistry, Ljubljana, Slovenia


This is a project to build supercomputing facilities on a low budget. It is based on Beowulf clusters and 2D, 3D torus, or other point-to-point–based parallel architectures, which avoids expensive network switching technology. This puts some restrictions on the efficient programming for such systems, but VRANA system becomes fully non-blocking fast Ethernet switch. There is also no limit on the number of processors, and the total throughput of the network scales linearly by the number of processors. All our systems were previously running Debian GNU/Linux but later we switched to Gentoo GNU/Linux. However any other distribution could be run as well.


First implementation of ideas and programs which support the network of independent workstations were done back in 1992. At that time I worked at NIH and we put up a cluster of HP workstations with the FDDI network. At around the same time we put up a cluster of HP workstations also at the CMM in Ljubljana. The network itself was not parallel but since single processor speed was not that high we managed to get a speedup of over 6 using 8 machines with our primary application CHARMM. The emergence of cheap 100 Mbit/sec network controllers started a new era of clusters around 1995-96. Beowulf and others were born.

The VRANA project at CMM started with model VRANA-1, which includes 4 dual processor Pentium II/400MHz boxes. They are connected in a ring topology. Each box has 3 Fast ethernet controllers. The details of the setup for such cluster are available.

VRANA-2 model was build from the computers which are used by students in a computer class. It consists of 16 single processor machines. The processor is Pentium II/450MHz. It is a 2D torus parallel architecture. Each box has 3 fast ethernet cards and one 10BT for the ``other'' system. The schematics of connections under the floor and other details are available on this page.

Model VRANA-3 is 32 processor (Celeron 466MHz) system. It was supposed to be 3D torus but it turned out a 2D MESH architecture, because Abit motherboard shares bus-mastering on the two of the five PCI slots, so only 4 fast ethernet cards are in each box.

Model VRANA-4 benchmark timings are available This time we successfully put 6 100 Mbit/sec network controllers in each box (one processor per box) which enabled us to build a 6 dimensional hypercube avoiding to buy an expensive non-blocking 70 port fast ethernet switch. In order to manage all these connections a program was written which builds the network setup file (/etc/network/interfaces) for each of the boxes automatically. The program is available here and can be compiled with gcc -o hc hc.c. One must run it with one command line parameter which specifies the dimension of the hypercube. It works for any dimension from 0 to infinity and it is pretty well documented. It also draws the cable (or better interface) connections between all the boxes using vcg. I would like to hear about if there are any bugs or comments on the program. The installation of these files is as easy as:

for i in `seq 64`;do rsh v$i rcp v1:/root/interfaces-v$i /etc/network/interfaces;done
To run it one can do:
for i in `seq 64`;do rsh v$i ifup -a;done  # Good for Debian and perhaps RedHat.

VRANA-8 consists of 64 dual 1.8GHz athlon CPU boxes connected with 3 24 port gigabit swtiches.

VRANA-9 consists of 64 dual 1.6GHz opteron CPU boxes connected with 2 48 port gigabit swtiches.

VRANA-10 consists of 37 dual 1.8GHz dual core opteron CPU boxes connected with 48 port gigabit swtich.

VRANA-11 consists of 26 dual 1.8GHz quad core Core2 CPU boxes connected with the 48 port gigabit swtich.

VRANA-11A consists of 20 dual 2.0 GHz quad core Core2 CPU (45nm) boxes connected with the 48 port gigabit swtich.

In 2009 we reconfigured VRANA-11 system so it now consists of: 10 dual Xeon E5320, 7 dual Xeon E5405/10, and 5 dual Xeon 5420 processors

We completed VRANA-12 system, which has 77 dual Xeon E5520 boxes, and also VRANA-13 which has 14 dual AMD-6128 boxes and 12 quad AMD-6128 boxes.


Current status of VRANA clusters

As of May 2008 we are running clusters VRANA-8, VRANA-9, VRANA-10, VRANA-11, and VRANA-11A. This amounts to over 700 cores.

As of January 2011 we are running clusters VRANA-10, VRANA-11, VRANA-12, and VRANA-13. This amounts to over 1500 cores.

As of October 2018 we are running clusters VRANA-11, VRANA-12, VRANA-13 VRANA-14, and VRANA-15. This amounts to over 3000 cores.

Some guidelines in building your own cluster

What type of network? (now mostly obsolete)

Links to similar systems


Performance comparison of parallel computers.

This page is maintained by Milan Hodoscek.