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Not how it works. If you service has that 99.999% availability and you get a single unavailability event in a year, that's already 5 minutes of downtime complet
by zzzcpan 8y ago
Not how it works. If you service has that 99.999% availability and you get a single unavailability event in a year, that's already 5 minutes of downtime completely independent from all other events that users may or may not experience, there is almost no chance of overlap between them. Users definitely notice that. And worse, events are going to be even less frequent than that and ever more noticeable and on top of that you are going to underestimate actual unavailability by at least an order.
So, can we get to the level where unavailability is actually an unnoticeable noise? Yes, but definitely not the way Google does things. I'd generalize that Google is absolutely not the place to look for ideas on reliability.
- notyourwork 8y agoI think you have a misconception on what actual reliability is for more products and services. 99.999% is a solid service, 99.99999% is a hard to achieve target for enterprise software. To say Google is not the place to look for reliability is a pretty comical statement.
- zzzcpan 8y agoI don't have a misconception. Can you name a single internet service that has an actual five nines availability? That's definitely not google search nor gmail.
- notyourwork 8y agoI never claimed Google has 5 9s. Your claim that 99.999% for Gmail means Google isn't a place we should go to for reliability advice is comical at best, ignorant at worst.
- zzzcpan 8y agoI couldn't make that claim, because Gmail is very far from 99.999%. I merely pointed out that SRE quote is wrong, that's the quality of reliability advice they give. I generalized it, because I've seen plenty of bad reliability advices coming from Google, even burned by some of them in the past. If you are into reliability you really shouldn't take Google seriously.
- umanwizard 8y agoWhat specifically are you disagreeing with in the quote? It does not say that Google is five nines, nor does it say whether or not five nines is desirable. The argument is basically the following: (1) Consider the claim that getting to 100% reliability is important. (2) If the claim were true, then it would be important to go from 99.999999999999999% availability to 100%. (3) That is obviously not important, so the claim must be false. (4) Since we have shown that the best target value is not 100%, it must be some number x, with x < 100%.
- deleted 8y ago[deleted]
- mrep 8y agoGoogle cloud spanner has an availability SLA of 5 9s if you use multiple regions [0]. Not cheap though. [0]: https://cloud.google.com/spanner/sla https://cloud.google.com/spanner/sla
- joshuamorton 8y agoFor reference, 99.999 is 5 mins of downtime/year. 99.99999 is 3 seconds of downtime/year. As you get beyond 5 nines, environmental factors begin to dominate (if the service is networked: network unavailability, if the service is onsite, power outages and weather) any reliability inherent in the service.
- extropy 8y agoAny pointers to where to look for good reliability examples in software world? Genuinely curious.
- x3tm 8y agoI suppose a good example is whatever runs in NASA's control room or (to a lesser extent?) in control towers.