Storage backend compatibility

Some storage backends do not support all the features of S3:

Atmos

• does not support multi-part upload

Azure

• limits container names to 63 characters and restricts character set to lowercase alphanumeric and dash
• maximum multipart upload size of 195 GB, see JCLOUDS-1223
• does not support Expires header but does support Cache-Control header
• does not support object-level access control
• does not allow arbitrary list markers, partially emulated by mapping the last key to the opaque marker
• does not return ETag as an MD5 hash, instead returning opaque data

B2

• bucket names must be between 6 and 50 characters and consistent of only letters, number, and hyphens
• requires buffering PUTs to calculate required SHA1 hash
• does not return ETag as an MD5 hash, instead returning SHA1 hash
• does not support blob-level access control
• does not support conditional GET
• does not support copying objects
• does not support Content-Disposition, Content-Encoding, Content-Language, Content-MD5, or Expiry headers
• multipart upload requires at least 2 parts

filesystem

• does not support listing in-progress multipart uploads
• does not support object metadata on Mac OS X, see JDK-8030048
• does not support object metadata using Docker and aufs, see docker/docker#1070

Google Cloud Storage

• does not allow arbitrary list markers, partially emulated by mapping the last key to the opaque marker
• does not return ETag as an MD5 hash, instead returning opaque data
• limits multi-part uploads to 32 parts

OpenStack Swift

• does not support Content-Language headers
• does not support copying objects with the If-None-Match header
• does not support deleting user metadata keys, only replacing them
• does not support object-level access control
• exposes multipart upload parts as regular keys