Cloud storage is designed for 99.999% annual durability, ideal for primary storage and business-critical applications. This level of durability is provided by Eraser encoding, which stores data redundantly among multiple devices in multiple Availability Zones. Before verifying writes, objects created in Cloud Storage must be copied in at least 2 free spaces. Checksums detect data integrity of all stored, periodically revalidated, and stored data. It will be corrected automatically with redundant data if necessary. Customers can optionally enable the versioning of objects to add protection against accidental deletion.