5 Ways to Make
Your Capacity Plan Bullet Proof
By: Ivan Walsh
This week’s article on Capacity Planning looks at the
'Assumptions' you need flag in your plan.
Assumptions are something you need to flag in the
introduction to your Capacity Plan. You can’t take anything for granted in an IT
Dept, or if there are third parties involved. Flag these upfront and cover
yourself.
As Al Pacino says in Insomnia, “It’s your name that goes on
the report.” Hilary Swank knew what he meant and double-checked everything.
Same applies to you – it’s your career, after all.
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to download your Capacity Plan template
Writing a Capacity Management Plan is easier than you’d
think. Most people avoid it and leave it to last. It’s also part of ITIL
umbrella, which has a reputation for being obscure, difficult and heavy on
paperwork. Capacity Planning is one of those documents that nobody wants to
write, but once you get into it, it’s fine.
1. Why do I need to Identify
Assumptions?
In the Introduction chapter of your Capacity Plan, you need
to:
Identify assumptions so that the Project Stakeholders and
those who will sign-off on this document fully understand the limitations,
constraints or conditions that underpin the plan.
As you are responsible for the content of this document,
it’s up to you to ensure that you have covered all angles so that if the
Capacity Plan needs be changed, you can point out that this issue was raised in
the Assumptions section.
Identify conditions relating to business scenario that may
require capacity (i.e. technical resources) and how your calculations for these
figures were derived.
Highlight assumptions which are beyond the control of the
project but may influence its success.
Failure to identify assumption leaves you in a delicate
position if the project stakeholders question that performance of your system,
for example, its inability to manage heavy loads during peak periods or your
dependence on a third party software.
If you're dependent on this, flag it here.
2. What are Assumptions?
Assumptions describe assumed factors (as opposed to known
facts) that could undermine the information in this document and disallow you
for implementing your Capacity Plan successfully.
Click here
to download your Capacity Plan template 3.
Examples of Assumptions?
Example of typical Assumptions include:
- Third-party software that you rely on
- Operating environment that is outside your control
- Company policy that determines how users access, use and
interact with the system
- Legislation that may change and effect your system
configuration
The Capacity Plan model could be negatively affected if
these assumptions are incorrect or change during the project lifecycle.
4. How to Write Assumptions?
All Assumptions have a potential Impact.
When you write your assumptions, word it so that you
identify the Assumption and then describe the Impact it will have on your
Capacity Plan.
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to download your Capacity Plan template
5. Examples of Common Assumptions
Here are some examples:
Assumption - Server utilization is limited to 75%
Impact - The server capacity sizing has been performed with
the assumption that the system performs within the SLA criteria.
Assumption - Changes in Programs
Impact - This Capacity Plan does not account for
performance impact of changes made to the system beyond those implemented by
[enter date]. Adding new programs to existing programs will affect the
application resource utilization.
Assumption - Change in Hardware Usage
Impact - This Capacity Plan assumes no changes in hardware
due to modifications to program usage. Changing user programs and other
application configurations will impact batch and online execution times.
Assumption - Changes in Business Processes
Impact - This plan assumes no change in performance
characteristics due to changes in business process. Changes in business process
may affect the execution of Batch Jobs.
Assumption - Topology Changes
Impact - This plan assumes no performance impact due to
topology or architectural changes.
Assumption - Database Capacity
Impact - It is assumed that the processor utilization
during batch processing will be the driving factor for database capacity. The
March 2010 batch cut-off CPU utilization data validates this assumption.
The average Daytime CPU utilization was 66% while the
average Night-time CPU utilization batch cycle was 386%.
Assumption - Accuracy of Load Data for Email Services
Impact - There is insufficient information regarding load
volume from email services, which share hardware with application server for
online and other services.
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to download your Capacity Plan template
There is also insufficient data on growth of the
email services load. The current capacity model does not separately account for
email services for capacity estimation.
Assumption - Hardware Estimates
The baseline for creating the capacity estimate model is
determined by the production resource utilization and transaction load data.
Assumption - Online transactions are processed in real
time.
Impact - The peak transaction load is the limiting factor
when estimating requirements for the application servers.
Assumption - Batch Processing will be process transactions
in off line mode.
Impact - Batch jobs can be controlled to balance the load
on servers. This means that average CPU utilization will be used for capacity
planning on these servers.
These are all examples of assumptions that you may need to
flag when writing your Capacity Plan.
What do you think?
If you were writing a Capacity Plan what would be the most
important points, you’d cover? How else can I place the document in context so
that the reader understands the scope of this exercise?
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to download your Capacity Plan template
What have I missed?
What mistakes do people make when scheduling batch runs and
when factoring this information in the Capacity Plan?
About Ivan
Ivan Walsh helps companies like yours improve their
technical documents. What’s the one question about technical writing you’d like
him to answer? Ask him at
www.ivanwalsh.com
PS - Click
here to download this
40 page MS
Word template instantly.
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