Amazon just recently announced a “Reduced Redundancy Storage” option for S3 objects. In short, you can slash the costs of S3 storage by 33% by accepting a slightly greater chance of losing your data. So ask yourself…
Do I feel lucky? Well, do ya, punk?
In truth, the costs of any data loss in Amazon S3 are minuscule, under both the traditional model and under RRS. If you use S3, I highly recommend starting with the Vogels’ article on RRS and durability.
The same goes for durability; core to the design of S3 is that we go to great lengths to never, ever lose a single bit. We use several techniques to ensure the durability of the data our customers trust us with, and some of those (e.g. replication across multiple devices and facilities) overlap with those we use for providing high-availability. One of the things that S3 is really good at is deciding what action to take when failure happens, how to re-replicate and re-distribute such that we can continue to provide the availability and durability the customers of the service have come to expect. These techniques allow us to design our service for 99.999999999% durability.
Under RRS, instead of 99.999999999% durability, your object is only stored in such a way that is will survive a single data loss, or 99.99% durability:
We can now offer these customers the option to use Amazon S3 Reduced Redundancy Storage (RRS), which provides 99.99% durability at significantly lower cost. This durability is still much better than that of a typical storage system as we still use some forms of replication and other techniques to maintain a level of redundancy. Amazon S3 is designed to sustain the concurrent loss of data in two facilities, while the RRS storage option is designed to sustain the loss of data in a single facility. Because RRS is redundant across facilities, it is highly available and backed by the Amazon S3 Service Level Agreement.
Yes, it’s still covered by the SLA! Finally, to summarize the real risk in terms your manager can undterstand, take this from the RRS announcement on the AWS blog:
The new REDUCED_REDUNDANCY storage class activates a new feature known as Reduced Redundancy Storage, or RRS. Objects stored using RRS have a durability of 99.99%, or four 9’s. If you store 10,000 objects with us, on average we may lose one of them every year. RRS is designed to sustain the loss of data in a single facility.
I suspect that for most business applications 99.99% durability is “good enough” and a 33% savings cost is an great trade-off.