This page discusses concepts related to data availability and durability in Cloud Storage.
Cloud Storage is designed for 99.999999999% (11 9's) annual durability.
To achieve this, Cloud Storage uses erasure coding and stores data pieces redundantly across multiple devices located in multiple availability zones.
Cloud Storage redundantly stores objects that are written to it in at least two different availability zones before considering the write to be successful.
Checksums are stored and regularly revalidated to proactively verify the integrity of all data at rest as well as to detect corruption of data in transit. If required, corrections are automatically made using redundant data.
The monthly availability of data stored in Cloud Storage depends on the storage class of the data. For more information, see available storage classes.