title: AWS S3: IA vs One-Zone IA Storage Classes
body: <p>Amazon announced on April 2018 the availability of a new storage class, named One-Zone Infrequent Access, that complements the plain IA option by lowering the cost via the usage of only one AZ for storage.</p>
  
  <p>Its <a href="https://aws.amazon.com/about-aws/whats-new/2018/04/announcing-s3-one-zone-infrequent-access-a-new-amazon-s3-storage-class/" rel="nofollow noreferrer">site</a>, advertises that <strong>all</strong> storage classes have the so-called 11 9s durability.</p>
  
  <p>My question is how two options (IA vs One Zone IA) can have the same (i.e. 11 9s) durability, given that the later uses 1 AZ (vs multiple of the former)</p>
  
  <blockquote>
    <p>Amazon S3 Standard, S3 Standard-IA, S3 One Zone-IA, and Amazon
    Glacier, are all designed for 99.999999999% durability. Amazon S3
    Standard, S3 Standard-IA and Amazon Glacier distribute data across a
    minimum of three geographically-separated Availability Zones to offer
    the highest level of resilience to AZ loss. S3 One Zone-IA saves cost
    by storing infrequently accessed data with lower resilience in a
    single Availability Zone.  Amazon S3 Standard-IA is a good choice for
    long-term storage of master data that is infrequently accessed. For
    other infrequently accessed data, such as duplicates of backups or
    data summaries that can be regenerated, S3 One Zone-IA provides a
    lower price point</p>
  </blockquote>
  
  <p>ps. I think they are themselves implying that one zone has lower durability.</p>
  
  <blockquote>
    <p>One Zone-IA saves cost by storing infrequently accessed data with lower resilience in a single Availability Zone</p>
  </blockquote>