Durability is defined simply as how safe the data is and whether it would be possible to get the data back. How do we say that S3 One Zone-Infrequent access has 11 9’s of durability, given that it is stored in only one zone, there is a possibility of losing the data?
Welcome to the course. That is a great question! Per Amazon, they’ve designed S3 One Zone-IA for 99.999999999% durability for objects in a single Availability Zone. Because S3 One Zone-IA stores data in a single AWS Availability Zone, data stored in this storage class will be lost in the event of Availability Zone destruction. Given that, S3 One Zone-IA should only be used for storing secondary backup copies or easily re-creatable data.
All S3 storage classes have 11 9’s of durability from the documentation (https://aws.amazon.com/s3/storage-classes) except for the S3 RRS. Durability refers to the possibility that the object will remain "intact" after one year. Durability can be imparted by device failures, fires, theft, meteor strikes, earthquakes, or anything that can damage the drives in a data center.
I believe AWS can guarantee 11 9’s for durability in S3 One-Zone-1A because AWS can vouch for its drive quality, security layers of the data centers. The case is different for availability which refers to accessibility and uptime.
Hi Sundar, so remember that an Availability Zone still contains multiple data centers. Data using S3 One Zone-Infrequent access will still be replicated across data-centers within its one availability zone, and still will be available to achieve the 11 9s of durability through these means. However, in an event that a catastrophe occurs such that multiple data centers within an availability zone are destroyed, there is a possibility of the data being lost. However I don’t think this has ever happened.