[Catalyst] FW: Clustering catalyst apps

Wade.Stuart at fallon.com Wade.Stuart at fallon.com
Mon May 8 20:06:56 CEST 2006

catalyst-bounces at lists.rawmode.org wrote on 05/08/2006 10:30:03 AM:

> Hi Gert, I think the key here is "average small company".
> My gut feel is that two relatively cheap rented servers at different
> datacentres using an (admittedly) crude DNS approach is enough to run
> small companies' web services reliably and cheaply.
> I'm not sure if you need more. The sort of questions I'd ask about your
> customer are:
> How much money are they willing to spend per month?
> Is it online retail or chat-based or some other service?
> How many transactions per hour are they handling?
> Is timeliness critical?
> Do they handle a few big customers who need perfect service, or many
> customers where they can afford to lose a few due to downtime?
> Assuming you do need more, there are a couple of aspects
> 1) Scalability
> 2) Reliability

Another thing you can do, and I have actually just seen this done first
hand (sad)
is figure out what the lowest percentage uptime that customers will not
baulk at for an SLA.

Lets say you choose 94% uptime.

Now, figure in how many hours your environment will be down per week.

68 hours?

ok,  that puts you way below 94% uptime.  So now start removing hours from
a 24x7 week.

Start with the weekends -- they are expendable (who uses applications on
the weekend) -- this gets you "free" 48 hours of downtime per week.

94% on 24x5, But you are still way below your 94% uptime SLA number. Just
calculate how many hours you need to lose from 24x5 to get to 94%.  In this
case about two per day.

So put 94% uptime based on 22x5 in your SLA.

Sounds good on paper, when you do the math looks like 61.3% uptime though
on a 24x7 schedule.

Of course I am being facetious, I have just had these exact numbers given
to me for one of our vendors services -- gogo outsourcing.


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