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Why You Need to Consider a Single-System Image : Page 2

SSI makes perfect sense for some, but this greatness comes at a great cost: years of work.


Do I really need it?

Often enough, having a single-system image does not make sense. You may want pockets of discrete resources, each serving its own master. This scenario often happens as a result of these three things:

    -          Monetary – people like the idea that what they paid for is not being used for someone else

    -          Political – sometimes folks just don’t want to be part of a larger and organized infrastructure that will force them to share the success and failures of others

    -          Technology – proper technology is not in place to allow such infrastructure to be built

These three and possibly others could be the culprit of why an enterprise-wide infrastructure is not deployed at times.

Segmenting a single-system seems like an oxymoronic way of approaching the problem, but it will make the users happy.  The idea is that a single infrastructure is built-out, but access to the infrastructure is controlled by many entry points as shown in figure 3.

Figure 3: Segmenting a Single-System

From the users’ perspective, each has a dedicated environment.  From the infrastructure management point of view, there is a single infrastructure.  AS one might expect, this is not ideal as the resource manager makes the best decision from what it knows and not a global view – commonly known as the local maxima problem.


SSI makes perfect sense for Grid, but this greatness comes at a great cost: years of work.  This is a repetitive process, where at times, one needs to take a step back in order to take two steps forward.  Keep in mind that a single-system-image can only be achieved if the idea is sold to the users and all participants see the benefit that it brings.

Art Sedighi -- Contributing Editor, Cloud, HPC and Grid -- is a freelance writer and IT consultant. Mr. Sedighi was the CTO and founder of SoftModule and held the senior consulting engineer position at DataSynapse. He received his BS in Electrical Engineering and MS in Computer Science, both from Rensselaer Polytechnic Institute.
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