Added by Jacek Becla, last edited by Kian-Tat Lim on Jan 29, 2009  (view change)

Labels:

Enter labels to add to this page:
Wait Image 
Looking for a label? Just start typing.

This page discusses IO/CPU/memory balance for data-intensive extreme-scale systems.

Amdahl's Laws

The Amdahl's Law, which is now over 40 years old, defines ratios in a well balanced system. A question arises: does the law still apply to today's systems, and if so, what ratios work well for data-intensive extreme-scale systems?

The law:

  1. Amdahl's parallelism law: If a computation has a serial part S and a parallel component P, then the maximum speedup is S/(S+P).
  2. Amdahl's balanced system law: A system needs a bit of IO per second per instruction per second.
  3. Amdahl's memory law: alpha=1: that is the MB/MIPS ratio, in a balanced system is 1.
  4. Amdahl's IO law: Programs do one IO per 50,000 instructions

According to some sources, see [3], [4]:

Application type
Typically
running on
Amdahl number
(IO:CPU)
Amdahl number
(memory:MIPS)
High-performance-computing applications
supercomputer ~ 1E-05
 
Computation-heavy data-intensive simulations
Beowulf cluster
~1E-03  
Data-intensive analytical applications
Beowulf cluster
~1E-01 to ~1  

Survey of Existing or Planned Systems

  • GrayWulf: BW=0.5, MEM = 1.04
    (Dell 2950 Server, 8 core, 16 GB RAM, 15x750 GB SATA disks, dual disk controllers, Infiniband) x 12. See [5].
  • BlueGene: BW=0.001, MEM=0.12

References

  1. The 40th Anniversary of Amdahl's Law, Gene Amdahl
  2. Petascale Computational Systems: Balanced CyberInfrastructure in a Data-Centric World, Gordon Bell, Jim Gray, Alex Szalay
  3. Amdahl Numbers as a Metric for Data Intensive Computing, Alex Szalay
  4. Oliver Ratzesberger's blog on eBay system
  5. GrayWulf