If you were doing a formal (and critical) SLA, then you'd most probably detail each element of the service and it's individual impact on your business and therefore it's SLA and penalty clause. You would often have differing availability requirements at different times of the day (or week/month), a good example of this might be a bank, loosing 1 ATM on a mid week afternoon would have less impact than loosing it on Pay Day.

I would guess that most people offering an SLA actually have no idea what an SLA actually is or even have a clue how they can implement it. Most commercial SLA's will generally have maintenance windows and things like that and your SLA time will be x% of the agreed availability period, not x% of actual wall clock time.

Seeing the "demand" for APC style remote reboot switches and so many comments on reboot times in other forums, I would guess that many "hosts" have to reboot their systems frequently, this could easily consume all their SLA down time just in reboots.

I would suggest most hosts understanding of an SLA is very much like the way everyone offers 24*7 support and GB's of space for £/month. Unless a host publishes the exact criteria of the SLA and how it's measured, then you have no chance of getting anywhere.

Whose SLA would you call ideal?

For an SLA to be meaningful, it would need to be drawn up against both side's expectations. If you're a customer and just looking for high up-time, then buy a quality service rather than a cheap one, then you'll more than likely not have to invoke an SLA penalty.

If 5 or 10 mins downtime is going to cause significant impact to the business, then I would suggest that the business could afford to buy a better service in the 1st place.

There is a lot of talk about Uptime Guarantees and some hosts have that 100% Guarantee on their sites, but how are the things in reality? Is it possible to prove that this guarantee has been violated and get refund?

If you see 24 hour, 7 day a week, 365 days a year uptime guarantees be careful in 2008 - there's 366 days!

Simple... a secret day off for hosts on either the 29th Feb or 31st Dec. You've rumbled their plans though

Good one.

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