[lionkor]

I'm not sure what 100% uptime is supposed to mean. Zero downtime, thats like saying zero bugs - it's not going to happen. Even 99.9999% uptime would be realistic, but 100% is not happening. There are factors out of your control that you cant guarantee will not even be down 1ms per year.

How do you manage 100% uptime when your db is only going to be 99.9%? The latter is almost easy, the former, even if we assume 99.99999%, really really hard.

Just silly and may show that there are some unrealistic assumptions, maybe? Or maybe the team doesn't know much about reliability -- also concerning.

Just target six nines and be done with it, or something.

In may of last year, NPM was down to 99.8 for the month.

[lucacasonato]

The SLO (objective) is an uptime of 100%. That means that we have no error budget to use for scheduled maintenance or anything of that sort. This means that we can not use software in this hot path that would require scheduled maintenance (ie a relational database that requires periodic downtime for major version upgrades). We additionally minimize risk here: no code that is written by us sits in the path that targets 100% uptime. Ie if it breaks, its due to an upstream failure within Google's web serving infrastructure.

If we were to provide an SLA (an agreement, stating the minimum level of service to a customer) for this service, it would not be 100%. It would be 99.99%. This is to avoid risk. But we can still have a higher internal target than the provided SLA.

If we have to make all changes in a way that requires that we do not even have 8 seconds of downtime a year (but 0 seconds of downtime), that significantly changes how you design a system and roll out changes.

TLDR: SLA != SLO

[lionkor]

Hi, that makes sense, thank you - I didnt realize that this was meant in terms of "we have to choose technologies that never ever have to have maintenance", that would have been a better way to put it. Thanks :)

[paxys]

It's a goal, not a guarantee.

[lionkor]

Yes, but it means nothing. If the realistic version of that goal is 99.99%, thats not very good at all.

You wouldnt applaud me if I said my goal total comp was 1M, and then i went and got a job that pays 30k.

[internetter]

I would if you said your goal was 1M and you made 999,999