The UKSBSGUY.com server is on my home broadband connection and this means it does not get business availability.  Last night I had another 10 hours downtime and 8 hours earlier in the month.  This all sounds bad, but here is where you need to understand SLAs and what availability statistics mean.

If I have a 24x7 contract and I want high availability then this is how much downtime I can have through the year:

From this you can see that I am somewhere between 99% and 99.9%.  If I assume 24 hours downtime this year then I am at about 99.7%, which on a consumer service is pretty amazing.  Now, if someone offers you a service rebate then you need to consider the service period.  For example, if someone offers 99.9% every day and you have a whole days outage, that is 1 day in 365 that they have failed, so any rebate might be very small.  Also bear in mind that if the service hours reduces (eg 9-5) then the amount of down time that is in spec reduces, but the service could be available or closed outside the service hours.

Hopefully this helps point to what you need to know when offering or signing up to SLAs:

1. Over what period is the availability measured (remember it is possible to offer 99.99% from 9-5 and then 0% outside this, so beware)
2. What is the recourse that is offered if a SLA is missed and how does it fit in the bit picture
3. What is the cost / impact of taking an SLA
4. How do they manage with existing customers
5. What are the exceptions (eg telling you 2 weeks in advance that the service will be down for 8 hours might exclude that service from SLA measures)

that is it.  Obviously there are a couple of SLA and managed services kings out there such as Karl - http://smallbizthoughts.blogspot.com/2007/09/final-thoughts-managed-services-in.html and the two PALs in the UK (Vijay and Gareth)

ttfn

David