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ITIL :: View topic - Designing for availability
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Designing for availability
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asrilrm
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Joined: Oct 07, 2007
Posts: 441
Location: Jakarta, INA

PostPosted: Tue Feb 03, 2009 11:32 pm    Post subject: Re: Designing for availability Reply with quote

BorisBear wrote:
Our method of calculating whether we can deliver required availability is along the lines of 'resilient servers x network x routers x desktop.....etc' (i.e. the traditional straight out of an ITIL book view of designing for availability). This is far too simplistic for my liking as it doesn't account for the internal and external support required to keep these components running and to fix them when they go wrong.


Sorry Boris, I might have misunderstood the above quote.
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JoePearson
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Joined: Oct 13, 2006
Posts: 116
Location: South Africa

PostPosted: Tue Feb 03, 2009 11:43 pm    Post subject: Reply with quote

BorisBear wrote:
Hmmmm...not sure I agree. What if the service is up and down like a gigolo's bottom with each downtime period being just a few minutes. In my experience this can be an even worse customer experience.


Good point. Sorry if I gave a different impression. (I don't put forum posts through any release control process!)

That example supports my claim that you shouldn't focus purely on percentage availability: 30 outages of 2 minutes in a month can be much worse than one outage of 1 hour, but both could be about 99.5% availability. Only the business can answer, but only the provider, usually, can ask the right questions.
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Diarmid
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Joined: Mar 04, 2008
Posts: 1884
Location: Newcastle-under-Lyme

PostPosted: Wed Feb 04, 2009 2:26 am    Post subject: Reply with quote

Boris,

have you considered a Borg collective for support staff?
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"Method goes far to prevent trouble in business: for it makes the task easy, hinders confusion, saves abundance of time, and instructs those that have business depending, both what to do and what to hope."
William Penn 1644-1718
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UKVIKING
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Joined: Sep 16, 2006
Posts: 3318
Location: London, UK

PostPosted: Wed Feb 04, 2009 2:33 am    Post subject: Reply with quote

JoePearson

With your example, most NMS tools are set to 5 minutes.... so the multiple bounces w/in may note reacha reporting threshold... but may reach an activity log threshold

When I use to manage NOC we wold see links bounce like a women's beach volleyball game. nice non PC visual

The outages were lesss than 5 minutes so the NMS tool did not report
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John Hardesty
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Change Management is POWER & CONTROL. /....evil laughter
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JoePearson
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Joined: Oct 13, 2006
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Location: South Africa

PostPosted: Wed Feb 04, 2009 2:39 am    Post subject: Reply with quote

Hmm ... I'm going to design a new network monitoring tool which graphically shows bouncing links as you have suggested. Since I started typing this I've got 70 orders for it.
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BorisBear
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Joined: Mar 10, 2008
Posts: 403
Location: Sunderland

PostPosted: Wed Feb 04, 2009 3:41 am    Post subject: Reply with quote

Diarmid wrote:
Boris,

have you considered a Borg collective for support staff?


We did once outsource to Androids (you decide who this was) - to be fair it had the desired effect.
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UKVIKING
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Joined: Sep 16, 2006
Posts: 3318
Location: London, UK

PostPosted: Wed Feb 04, 2009 3:45 am    Post subject: Reply with quote

I would rather outsource to Altoids

At least their breath is fresh, unlike the the SD scottsih terriers in book 6

Maybe a new chapter or section is needed

Breath Mints for the SD staff
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John Hardesty
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Change Management is POWER & CONTROL. /....evil laughter
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asrilrm
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Joined: Oct 07, 2007
Posts: 441
Location: Jakarta, INA

PostPosted: Wed Feb 04, 2009 9:11 am    Post subject: Reply with quote

I thought Wookies were much better than androids or altoids whatsoever Surprised
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UKVIKING
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Joined: Sep 16, 2006
Posts: 3318
Location: London, UK

PostPosted: Wed Feb 04, 2009 4:57 pm    Post subject: Reply with quote

Altoids are a a brand name for a Breath mint that is rather strong

Wookies shed too much hair andsome people are allergic t the hair in the NOC
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nasz
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Joined: Jun 18, 2007
Posts: 10
Location: Adelaide, South Australia

PostPosted: Thu Apr 15, 2010 10:54 am    Post subject: Reply with quote

May as well add my own two pennies worth!

Availability of the component is the percentage of time when system is operational. Availability of a hardware/software component can be obtained by the formula given below.

A=MTBF/(MTBF+MTTR)

Example 01:
If we are using equipment which has ‘Mean Time Between Failure’ (MTBF) of 81.5 years and ‘Mean Time To Recovery’ (MTTR) of 1 hour:
MTBF in hours = 81.5*365*24=713940
Availability= MTBF/(MTBF+MDT) = 713940/713941 =99.999859%
Unavailability = 0.000141%
Outage due to equipment in hours per year
Unavailability =0.01235 hours per year.

Whereas, availability of an IS service or system (a combination of hardware/software components) is the percentage of time when the service is operational. Availability of an IS service can be obtained by the formula given below:

A=Uptime/(Uptime +Downtime)

Example 02:
If an IS Service has an agreed uptime of 200 hours for a 30 day period (M-F 0800-1800hrs) and was not available for 3 hours during that time the availability of that IS Service is 98.52% for that period.

200/(200 +3)=0.9852 or 98.52%

However, when an IS Service is utilised by several different business units; and each unit has an individual SLA on place with IS Operations, the following formula can provide a means of calculating the end-user availability of a specific group, region or location, where the IS Service is delivered:

(Agreed Hours* No.of Users-Sum of (incident x Duration* % of users affected))/(Agreed Hours* No.of Users)*100

Example 03:
If an IS Service has an agreed uptime of 200 hours for a 30 day period (M-F 0800-1800hrs) and has a user community of 1000 users in four locations (Each location has 250 users) and one location experiences a single outage of 3 hours. Therefore the end-user availability of that IS Service is 99.625% for that period.

(200 *1000-(3 x 25%) )/(200*1000)*100=99.625 or 99.635%

Availability is typically specified in nines notation. For example ‘3-nines’ availability corresponds to 99.9% availability. A ‘5-nines’ availability corresponds to 99.999% availability.

Availability will be shown in service terms, as opposed to component, system or server terms as the business does not see the component level. All they know is that the email service is unavailable for example. This change in perception of unavailability will help drive IS to be more customer focused.
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