Overview of Cloud Storage Systems

Each cloud storage system is slighly different. Rclone attempts to provide a unified interface to them, but some underlying differences show through.

Features

Here is an overview of the major features of each cloud storage system:

Name
Hash
ModTime
Case Insensitive
Duplicate Files
Google Drive
MD5
Yes
No
Yes
Amazon S3
MD5
Yes
No
No
Openstack Swift
MD5
Yes
No
No
Dropbox
-
No
Yes
No
Google Cloud Storage
MD5
Yes
No
No
Amazon Cloud Drive
MD5
No
Yes
No
Microsoft One Drive
SHA1
Yes
Yes
No
Hubic
MD5
Yes
No
No
Backblaze B2
SHA1
Yes
No
No
Yandex Disk
MD5
Yes
No
No
The Local Filesystem
All
Yes
Depends
No

Hash

The cloud storage system supports various hash types of the objects.
The hashes are used when transferring data as an integrity check and can be specifically used with the –checksum flag in syncs and in the check command.

To use the checksum checks between filesystems they must support a common hash type.

ModTime

The cloud storage system supports setting modification times on objects. If it does then this enables a using the modification times as part of the sync. If not then only the size will be checked by default, though the MD5SUM can be checked with the –checksum flag.

All cloud storage systems support some kind of date on the object and these will be set when transferring from the cloud storage system.

Case Insensitive

If a cloud storage systems is case sensitive then it is possible to have two files which differ only in case, eg file.txt and FILE.txt. If a cloud storage system is case insensitive then that isn’t possible.

This can cause problems when syncing between a case insensitive system and a case sensitive system. The symptom of this is that no matter how many times you run the sync it never completes fully.

The local filesystem may or may not be case sensitive depending on OS.

Windows - usually case insensitive, though case is preserved
OSX - usually case insensitive, though it is possible to format case sensitive
Linux - usually case sensitive, but there are case insensitive file systems (eg FAT formatted USB keys)
Most of the time this doesn’t cause any problems as people tend to avoid files whose name differs only by case even on case sensitive systems.

Duplicate Files

If a cloud storage system allows duplicate files then it can have two objects with the same name.

This confuses rclone greatly when syncing - use the rclone dedupe command to rename or remove duplicates.