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Pertemuan 26Review Project

Matakuliah : H0204/ Rekayasa Sistem Komputer

Tahun : 2005

Versi : v0 / Revisi 1

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Learning Outcomes

Pada akhir pertemuan ini, diharapkan mahasiswa

akan mampu :

• Menguraikan Rekayasa sistem berdasarkan paparan project / studi kasus

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Outline Materi

• Paparan hasil project dengan Simulasi Software Kehandalan sistem (Relex Software / Reliability Expert) http://www.relexsoftware.com/

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Modeling Goals• The system reliability requirement is an availability of 0.9999 for 80%

of the users. This requirement can be further analyzed as follows:1. The network availability goal is specified at a certain level of service

delivery. Therefore, the system can operate at a degraded state and still achieve the network availability goal.

2. The metric for performance as stated in the specification is "Number of Connected Users." In our model, this translates to "Percentage of Total System Capacity". A capacity of 80% is equivalent to 80% of the users being connected.

3. The required availability is stated at the degraded operating point. Therefore, the software must be able to calculate the availability of 0.9999 at 80% capacity. Relex OpSim is capable of calculating availability at any capacity percentage desired.

4. The model should take into account the redundancy inherent in the components (in this case, the backbone switches).

5. It may be desirable to model the complete interconnections between the different components. While this is possible, it will complicate the model. For the purposes of this brief, these connections have been ignored. Due to the high MTBF and low MTTR of the connected components, the probability of connecting elements failing is extra-ordinarily low (MTBF of connection is >40,000,000 hrs).

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Modeling Process

• Please note that this is a sample process used to model the system in incremental steps. Once a user gets more familiar with the software, it will be possible to perform the modeling steps in less of a sequential path.

• Determine the total number of users so that component contributions can be determined. The total number of users in this example is 525. Therefore, each RJ45V Card on the ITN22 backbone will support 23/525 = 4.38% of the total capacity (assuming that they are equally loaded).

• Create and connect the blocks for the RJ45V path as shown below: – The green blocks are the components in the system, and can have

MTBFs, repair times and capacities (as well as many other values) assigned to them. Components may only have one input or output.

– The purple blocks are junction nodes, and can have any numbers of inputs or outputs. The type of junction can be specified as well. For instance, the Power Supplies (PS) blocks are connected using 1 of 2 parallel operating redundancies, and the Supervisor cards (S1 and S2) are connected using standby redundancy.

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• Assign the MTBF and repair properties to the blocks above. All capacities are set to 100% except for the RJ45 cards, which were set to 4.38%.

• Create and connect the blocks for the GBIC connection, as shown next:

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• Enter the data for the new components. Note that the Chassis and Power supplies shown leading into the GBIC card are "repeats" of the initial components. This is because they are exactly the same components. "Repeats" share the same properties, fail, and are repaired at exactly the same time as the originals. Of the new components, the Assy: 3548, PN: GBIC components (on the bottom right) are the only components with capacities other than 100%. Their capacities are 30/525 = 5.71%.

• Copy and paste the system, then alter data where required, to create the final system as shown here:

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• Please note that the End node is a parallel operating node, with only 1 of the 20 incoming paths required for the system to operate. The required capacity is set during calculation. Changing requirements do not require a change to the model.

• At this point, the system was calculated, and it was determined that the system did meet the requirements specified. Results can then be print previewed in a report, then exported to Microsoft Word.

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