Overview of cloud storage systems

Each cloud storage system is slightly 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
Amazon Drive MD5 No Yes No R
Amazon S3 MD5 Yes No No R/W
Backblaze B2 SHA1 Yes No No R/W
Box SHA1 Yes Yes No -
Dropbox DBHASH † Yes Yes No -
FTP - No No No -
Google Cloud Storage MD5 Yes No No R/W
Google Drive MD5 Yes No Yes R/W
HTTP - No No No R
Hubic MD5 Yes No No R/W
Mega - No No Yes -
Microsoft Azure Blob Storage MD5 Yes No No R/W
Microsoft OneDrive SHA1 ‡‡ Yes Yes No R
OpenDrive MD5 Yes Yes No -
Openstack Swift MD5 Yes No No R/W
pCloud MD5, SHA1 Yes No No W
QingStor MD5 No No No R/W
SFTP MD5, SHA1 ‡ Yes Depends No -
WebDAV - Yes †† Depends No -
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 verify checksums when transferring between cloud storage systems they must support a common hash type.

† Note that Dropbox supports its own custom hash. This is an SHA256 sum of all the 4MB block SHA256s.

‡ SFTP supports checksums if the same login has shell access and md5sum or sha1sum as well as echo are in the remote’s PATH.

†† WebDAV supports modtimes when used with Owncloud and Nextcloud only.

‡‡ Microsoft OneDrive Personal supports SHA1 hashes, whereas OneDrive for business and SharePoint server support Microsoft’s own QuickXorHash.

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 and SFTP 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 ListR StreamUpload LinkSharing About
Amazon Drive Yes No Yes Yes No #575 No No No #2178 No
Amazon S3 No Yes No No No Yes Yes No #2178 No
Backblaze B2 No No No No Yes Yes Yes No #2178 No
Box Yes Yes Yes Yes No #575 No Yes No #2178 No
Dropbox Yes Yes Yes Yes No #575 No Yes Yes Yes
FTP No No Yes Yes No No Yes No #2178 No
Google Cloud Storage Yes Yes No No No Yes Yes No #2178 No
Google Drive Yes Yes Yes Yes Yes No Yes Yes Yes
HTTP No No No No No No No No #2178 No
Hubic Yes † Yes No No No Yes Yes No #2178 Yes
Mega Yes No Yes Yes No No No No #2178 Yes
Microsoft Azure Blob Storage Yes Yes No No No Yes No No #2178 No
Microsoft OneDrive Yes Yes Yes No #197 No #575 No No No #2178 Yes
OpenDrive Yes Yes Yes Yes No No No No No
Openstack Swift Yes † Yes No No No Yes Yes No #2178 Yes
pCloud Yes Yes Yes Yes Yes No No No #2178 Yes
QingStor No Yes No No No Yes No No #2178 No
SFTP No No Yes Yes No No Yes No #2178 No
WebDAV Yes Yes Yes Yes No No Yes ‡ No #2178 No
Yandex Disk Yes No No No Yes Yes Yes No #2178 No
The local filesystem Yes No Yes Yes No No Yes No Yes

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.

‡ StreamUpload is not supported with Nextcloud

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.

ListR

The remote supports a recursive list to list all the contents beneath a directory quickly. This enables the --fast-list flag to work. See the rclone docs for more details.

StreamUpload

Some remotes allow files to be uploaded without knowing the file size in advance. This allows certain operations to work without spooling the file to local disk first, e.g. rclone rcat.

LinkSharing

Sets the necessary permissions on a file or folder and prints a link that allows others to access them, even if they don’t have an account on the particular cloud provider.

About

This is used to fetch quota information from the remote, like bytes used/free/quota and bytes used in the trash.

If the server can’t do About then rclone about will return an error.

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