rclone/docs/content/overview.md

title	description	type	date
Overview of cloud storage systems	Overview of cloud storage systems	page	2015-09-06

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
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
Microsoft Azure Blob Storage	MD5	Yes	No	No	R/W
Microsoft OneDrive	SHA1	Yes	Yes	No	R
Openstack Swift	MD5	Yes	No	No	R/W
QingStor	-	No	No	No	R/W
SFTP	MD5, SHA1 *	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.

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
Amazon Drive	Yes	No	Yes	Yes	No #575	No	No
Amazon S3	No	Yes	No	No	No	Yes	No #1614
Backblaze B2	No	No	No	No	Yes	Yes	No #1614
Box	Yes	Yes	Yes	Yes	No #575	No	Yes
Dropbox	Yes	Yes	Yes	Yes	No #575	No	Yes
FTP	No	No	Yes	Yes	No	No	Yes
Google Cloud Storage	Yes	Yes	No	No	No	Yes	No #1614
Google Drive	Yes	Yes	Yes	Yes	No #575	No	Yes
HTTP	No	No	No	No	No	No	No
Hubic	Yes †	Yes	No	No	No	Yes	No #1614
Microsoft Azure Blob Storage	Yes	Yes	No	No	No	Yes	No
Microsoft OneDrive	Yes	Yes	Yes	No #197	No #575	No	No #1614
Openstack Swift	Yes †	Yes	No	No	No	Yes	No #1614
QingStor	No	Yes	No	No	No	Yes	No #1614
SFTP	No	No	Yes	Yes	No	No	Yes
Yandex Disk	Yes	No	No	No	No #575	Yes	Yes
The local filesystem	Yes	No	Yes	Yes	No	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.

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.