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Re: Limits of reliability or is 99.999999999% realistic

  • From: Marshall Eubanks
  • Date: Mon Nov 27 11:14:46 2000

[email protected] wrote:

> SLAs are the point where commercial & operational worlds collide. The numbers
> being offered should:
> Reflect the targeted quality of the service
> Tie in with meaningful damages for not achieving them
> In a market where I can offer 99.7% or 100% and the difference is a whole day's
> service credit, I know what I'd be offering. No question.
> If on the other hand, the expectation is that I pay out a year's contract value
> in cash upfront every time I miss a target in a month, then I'd only want to
> offer a target that will *always* be achieved.
> In the market at the moment, the situation is much closer to the first scenario
> than the second - ie damages for SLAs do not mean anything to either:
> the buyer, as compensation for not receiving the service that they have
> contracted for;
> or
> the seller as a motivation to work within the targets, because capped service
> credit agreements do not touch the bottom line
> Today, in the IP market, it is irrelevant whether services come with 99.0 or
> 99.99999 SLAs & at some point the market needs to address the responsibility
> that if they are to offer a service of a certain "guaranteed" quality, then they
> should stand-by that guarantee with their money and give this guarantee meaning.
> I don't think this is the case at the moment, and that's why we even see 100%
> SLA in the market - because the level of pay-outs on SLAs don't matter to the
> seller.
> No. I'm not suggesting that sellers offer guarantees for consequential losses.
> Simply ones that:
> 1. give the buyer the peace of mind that if the service they've contracted to is
> below par, that they will have enough money put back in their pocket for them to
> have replaced their service, like-for-like in the market, to cover themselves
> over the period.
> 2. enable the market players to truly differentiate their service offerings by
> quality, rather than marketing.
> Toby
> [std. disclaimer of responsiblity here]
> Date: 25 Nov 2000 20:24:48 -0800
> From: Sean Donelan <[email protected]>
> Subject: Limits of reliability or is 99.999999999% realistic
> <snipped for brevity>
> But back to my question.  What is the real requirement?  Amazon.COM had
> system problems on Friday, and their site was unusuable for 30 minutes,
> definitely not 99.999%.  But what did that really mean?  The FAA loses
> its radar for several hours in various parts of the country.  What did
> that really mean?  Essentially every system given as an example of "high-
> availability, high-reliability" I've looked at, doesn't hold up under
> close examination.
> Is 99.999% just F.U.D. created by consultants?
> Instead of pretending we can build systems which will never fail, should
> we work on a realistic understanding of what can be delivered?


This reminds me of arguments that we had in my former work involving deep spacecraft.

In spacecraft work, JPL has found that, if you did not
strive for "5 sigma's" or even "6 sigma's" of reliability, then
there would always be something you hadn't counted on that would
drive reliability to zero. In other words, planning for very high reliability makes
you do the engineering which gives you the redundancy which makes
it possible to withstand unexpected events without (too much) failure. To the extent SLA's
reflect that, they should be useful, regardless of how sound the statistics are.
                                 Marshall Eubanks

T.M. Eubanks
Multicast Technologies, Inc
10301 Democracy Lane, Suite 410
Fairfax, Virginia 22030
Phone : 703-293-9624
Fax     : 703-293-9609
e-mail : [email protected]     [email protected]