Day 20

Network/System Administrator• Plenty of jobs

– Not likely to be outsourced because you need physical access to the machines

• Challenging job– New problems every day, no 2 days

alike– Things tend to grow not shrink– Always have things to plan for

Network vs System Admin• System Admin typically deals with

just the desktop computers • Network Admins typically deal

with both the network and the servers

• Often these terms are not that cleanly cut.

Your job• In general any job has the

following traits– You should be providing the company

as much return as you take.• Sometimes things are difficult to quantify

– Easy to identify things like:» Customers» Money» Customer Satisfaction

• If not you’ll likely find yourself on the chopping block

Projects• Generally companies break things

up into projects– Easier to track

• Time• Expense• Progress

– Plus people feel like they are getting somewhere if a project ends and a new one begins

Project Cycle• Decide what you want to do

– Draw up Requirements Specification

• Design how you are going to do it– Draw up a Design Specification

• Do it– Implement your design

• Test and verify your implementation against your Requirements

If not => Failure• If you try to make changes to the

requirements mid way, your design will probably break

• Overruns in time and cost are typically caused by “Feature creep”

System Development Life Cycle• Planning• Analysis• Design• Implementation• Maintenance

Wash, Rinse and Repeat.

Planning• How much of something do you

need?– Do you need 10mb networking?

100mb? Gig ethernet?– Do you need 1 web server? 10?, 100?– Do you need the $40 switch, or the

$5,000 switch

• Overbuy?– Costs more

• Underbuy– You may lose your job in a failure– Or the system may fail

You are…the weakest link!• The weakest link takes down the

system– Often spend all the money on the

wrong things– You need all parts of the system to be

of equal capability otherwise it all runs as slow as its slowest part• E.g. You buy an OC48 externally, gig

networking, gig network cards, and have a single hard drive in a web server. The hard drive can only transfer at 30MB at best.

– Often sexiness determines which is a problem

Sometimes you have to guess• The Aquarium just opened

– Their website failed for 4 days, why?

• Sometimes you can calculate– If you know that your biggest

webpage is 100k, and you guess 500 people will hit it per second, you can now calculate things

Planning• Which to use (Min, Avg, Max)?• Is it possible?

– Technically?– In your area?– In the time you have?– With the money you have?

• Will it pay for itself– Consider productivity, – customer satisfaction, – cost of maintenance– Uptime payback

Uptime• Calculated by measuring how much you

are down– Sometimes you get this as a guarantee

• Take with a grain of salt. All it means is they’ll refund your money, little comfort if you lose your biggest customer

– 4 9’s• Means 99.9999% uptime• This means you have 8.6 seconds of down time

per day, 4.5 minutes per month.

– Some industries are regulated• Nuclear power plants often have 9 or 10 9’s

requirements.

• Mean time between failure

Baseline study• Monitor what you are doing now• This will help you know how things

will look in the future• Also lets you see non obvious

trends

SNMP• Allows you to monitor a network

– You can see utilization of resources• Network traffic• CPU usage• Memory usage• Disk usage

– You can monitor services• When sendmail fails it can trap

• Traps can be caught and generate:– Emails, pages, phone calls etc.