Explain Your Boss Advantages Of PC Clusters...
PC clusters now offer solution for affordable supercomputing. The role of traditional supercomputers
(like CRAY) was once taken over by workstations. Now the huge PC market allowed unprecedented
dynamics of PC hardware evolution. Good PC offers far the best price/performance ratio unavailable
with any workstation. Todays networking technology made PC clusters feasible computing tool
and allowed them to beat other technologies also in absolute numbers. The third major factor is
explosive growth of free software enabled by global Internet. Worldly collaboration became well
established and very productive paradigm of software engineering even for the most demanding tasks
like writing the whole UNIX operating system. Releasing all the source code made global testing
possible and for important programs raised the standards of software quality to level hardly
achievable by any company.
This new situation attracted attention of many groups with a need for high performance
computing. PC clusters became well recognized and practical supercomputing tools and they are
being succesfully built and used at universities and research sites all over the world.
In the near future we can expect wider use of PC clusters in the industry:
Thought the PC cluster architecture was designed to achieve top
computing power, it also has a potential to serve as a redundant
However promissing, the PC cluster technology is still new and not known to general public.
To harnes its power, decision makers need to be well informed about its benefits and its pitfalls.
Probably the most scarce resource in this domain is nor the hardware nor software but knowledgeable
system administrators. Acquiring one and creating optimal conditions for his work and sustained
selfeducation might well be the major factor.
PC cluster - What Is It?
It is a group of (for example 16) personal computers connected by a very fast network.
Dislike usual personal computers, cluster members have no individual displays, no keyboards,
even maybe no floppy disks. They do have fast processors, enough RAM, hard disks and fast
network cards. Fast switch is used for network interconnect.
Computers run Linux operating system - free implementation of UNIX. Standard Linux itself provides
enough to make the cluster usable. On the top of it, standard parallel programming tools
can be installed, yielding portability of programs between PC clusters and traditional
supercomputers. Some minor operating system improovements special for PC clusters also exist.
Alltogether, PC clusters architecture is similar to the one of nowaday supercomputers, but it
employs widely used components only (albeit their usual use is different). This ensures
good component quality and low (or even zero) price.
Three Times More For The Same Money
Thought direct comparisons with commercial solutions are difficult and do require
exact specification of tasks to be solved on the computers being compared, it can be estimated
that for scientific work you will get at least three times better performance with PC clusters
than you would get using any commercial workstations or supercomputers of equivalent price. Even
ratios as high as 10 or 15 are not uncommon as a result of these comparisons.
Commodity Well Known Hardware
Supercomputing PC cluster is composed of usual PC hardware.
Switch used for PC interconnect is a normal network component (but usually it is being used
in central parts of big networks only).
Thus the price can be much lower than the price of any specialised supercomputing hardware.
Thought technically speaking PC hardware is not "the best possible", market considerations
make it optimal.
Components are chosen from the best ones on the market, however the very top (like the fastest
processors available in limited amounts) is better avoided bacause of unreasonable price.
It is better to buy more of next-to-top parts instead.
Easy Hardware Service
PC hardware is well known. Many sites can manage instant service by replacing faulty parts
themselves. Otherwise there always is a lot of service companies to choose from.
Most of the software needed is free of charge, including source code. This includes complete
re-implementation of UNIX operating system, networking, graphical X-windows system, editors,
compilers, various scientific tools etc. (Example of free software known to general public
is TeX.) Software piracy not needed anymore.
Free Software May Be MORE Reliable
Serious scientific experiments proved that important freely available software (GNU utilities)
is considerably more stable than equivalent software produced by any commercial UNIX vendor,
including the most respectable international companies.
This is probably due to the fact that free software available with source code is debugged by
all the world's people (instead of just one company). And futhermore, authors of widely used free
software are usually excellent programmers.
Free Software Is Flexible
Free availability of all the source code makes it possible to modify any part of your system.
Free Software Is Ideal For Education
Every piece of the software source code may serve as invaluable source of knowledge - nothing
is hidden in compiled programs.
Not Dependent On One Company
All the components are commodity. Should one company fail to deliver it, there always is another.
Should you ever find that this solution is not good for your purpose, you can still use
the hardware as ordinary individual PCs. Your investment does not involve the risk of
buying promissing but too specialised and not suitable hardware.
There Is Really No Display? How Is It Used???
Users can connect to the cluster via network using any graphical X-terminal. For this purpose one
can use another PC, old workstation, or it is possible to put graphics to the cluster itself.
Who Is Able To Work On PC Cluster?
First of all, users should be able to use UNIX operating system. Good and cheap way to become
familiar with UNIX is to install Linux on a single PC. For many users this is nearly all what is
needed. Programmers who would like to learn more (and get more) could start with PVM.
How much does it cost?
Typical number seemes to be $50,000 for a 16-node cluster. The number is relatively constant
in time - later on it is optimal to use better parts, the performance is higher, but not the
price. Of course, all this is just blatant simplification, you can make cluster with 8 nodes
or 64 nodes...
Is PC Hardware Really So Powerfull?
Yes, it is. Sometimes you just cannot see it because it is being used with not so good
software. But however bad some operating systems might be, there is also positive side
of this: Slow software forced hardware improovements to compensate for this, and millions
of users were forced to make huge hardware investments. Those suffering users financed
unprecedented PC hardware boom. Now you just have to choose good operating system (e.g. Linux).
Another factor is workstation manufacturers' advertisement. For sure they will not tell
you that workstation era is over. They will rather let you think that powerfull people
can be recognised as users of their workstations.
PC clusters may become standard for scientific computing. The number of sites using
this type of machines is growing rapidly, and building and using PC clusters is becoming
easier with every new instalation - majority of cluster administrators is willing to share
their experience and new software tools they develop.
Big Warning For The Very End
Once again I must repeat - get good system administrator. There is still a piece of adventure
in using PC clusters and deep knowledge and daring are more important than amount of money spent
And one more warning regarding PC hardware. There is excellent PC hardware but this is not
to say that all PC hardware is good. In fact choosing the right PC hardware for your cluster
requires knowledge of the hardware itself, wide knowledge of the hardware market and also
detailed information about hardware support provided by Linux operating system. Consult well
informed hardware specialist before you buy.
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