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 MIME Type
Google Drive MD5 Yes No Yes R/W
Amazon S3 MD5 Yes No No R/W
Openstack Swift MD5 Yes No No R/W
Dropbox - No Yes No R
Google Cloud Storage MD5 Yes No No R/W
Amazon Drive MD5 No Yes No R
Microsoft One Drive SHA1 Yes Yes No R
Hubic MD5 Yes No No R/W
Backblaze B2 SHA1 Yes No No R/W
Yandex Disk MD5 Yes No No R/W
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.

MIME Type

MIME types (also known as media types) classify types of documents using a simple text classification, eg text/html or application/pdf.

Some cloud storage systems support reading (R) the MIME type of objects and some support writing (W) the MIME type of objects.

The MIME type can be important if you are serving files directly to HTTP from the storage system.

If you are copying from a remote which supports reading (R) to a remote which supports writing (W) then rclone will preserve the MIME types. Otherwise they will be guessed from the extension, or the remote itself may assign the MIME type.

Optional Features

All the remotes support a basic set of features, but there are some optional features supported by some remotes used to make some operations more efficient.

Name Purge Copy Move DirMove CleanUp
Google Drive Yes Yes Yes Yes No #575
Amazon S3 No Yes No No No
Openstack Swift Yes † Yes No No No
Dropbox Yes Yes Yes Yes No #575
Google Cloud Storage Yes Yes No No No
Amazon Drive Yes No Yes Yes No #575
Microsoft One Drive Yes Yes No #197 No #197 No #575
Hubic Yes † Yes No No No
Backblaze B2 No No No No Yes
Yandex Disk Yes No No No No #575
The local filesystem Yes No Yes Yes No

Purge

This deletes a directory quicker than just deleting all the files in the directory.

† Note Swift and Hubic implement this in order to delete directory markers but they don’t actually have a quicker way of deleting files other than deleting them individually.

Copy

Used when copying an object to and from the same remote. This known as a server side copy so you can copy a file without downloading it and uploading it again. It is used if you use rclone copy or rclone move if the remote doesn’t support Move directly.

If the server doesn’t support Copy directly then for copy operations the file is downloaded then re-uploaded.

Move

Used when moving/renaming an object on the same remote. This is known as a server side move of a file. This is used in rclone move if the server doesn’t support DirMove.

If the server isn’t capable of Move then rclone simulates it with Copy then delete. If the server doesn’t support Copy then rclone will download the file and re-upload it.

DirMove

This is used to implement rclone move to move a directory if possible. If it isn’t then it will use Move on each file (which falls back to Copy then download and upload - see Move section).

CleanUp

This is used for emptying the trash for a remote by rclone cleanup.

If the server can’t do CleanUp then rclone cleanup will return an error.

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