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> do with S3 to achieve 11 9's availability I see so many people confused about this. Eleven nines is their durability guarantee, their availability that they
by takeda 10y ago
> do with S3 to achieve 11 9's availability
I see so many people confused about this. Eleven nines is their durability guarantee, their availability that they guarantee is only 99.99%
https://aws.amazon.com/s3/faqs/ https://aws.amazon.com/s3/faqs/
- JumpCrisscross 10y agoWhat's the difference between durability and availability?
- gohrt 10y agodurability means you'll get your bits eventually. availability means you'll get your bits immediately.
- eloff 10y agoAvailability is the % of times you try to access your data that you get it back. So 52.5 minutes of downtime a year is still within SLA. Durability is the % of your data that doesn't die. Eleven 9s means that if you store 1TB on AWS S3 you can expect to lose 10 bytes and still be within SLA.
- jacquesm 10y agoNo, it means that if you store your data there that there is a .000000001% chance that you will lose all of it.
- speedplane 10y agoIs that true? How can they possibly measure a probability event so small? If every human in the world was their customer, then .05 humans would lost heir data?
- jontas 10y agoI don't know much about actuarial math but I think this number is for insurance policies more than anything else. It could be based on something like the rate of hardware failures they experience now amortized over a long period and many customers, and then adjusted to account for redundancy. As a very simplified example, imagine they are expecting to lose 2 servers every day, this percentage might be the probability of those two servers storing the same exact object (and thus, losing it irretrievably).
- hanoz 10y agoFor those wondering .000000001% per what? The answer apparently is per object year. i.e. you could expect to lose 10 bytes of your 1TB every year if your stored it as a trillion one byte objects, but if you stored it as a single object you could expect to lose the whole thing once every hundred billion years, but none of it the rest of the time.
- eloff 10y agoIt doesn't mean that either. It's just an SLA. Could have been a number pulled out of the air. Likely loss in real life would be granular at the object level.
- bogomipz 10y agoDurable means it was persisted to disk. Availability means the service is up and reachable.
- bogomipz 10y agoI hear this misunderstanding a lot as well, generally in relation to AWS S3 SLAs. 11 9's of "uptime" would mean service could be be down for 3 milliseconds a year. 4 9s is very respectable.