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
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	Partial	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.

Backblaze B2 preserves file modification times on files uploaded and
downloaded, but doesn't use them to decide which objects to sync.

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.