Matakuliah
Tahun
Versi
: H0204/ Rekayasa Sistem Komputer
: 2005
: v0 / Revisi 1
Pertemuan 26
Review Project
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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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