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| 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 | MD5SUM | ModTime | Case Insensitive | Duplicate Files |
|---|---|---|---|---|
| Google Drive | Yes | Yes | No | Yes |
| Amazon S3 | Yes | Yes | No | No |
| Openstack Swift | Yes | Yes | No | No |
| Dropbox | No | No | Yes | No |
| Google Cloud Storage | Yes | Yes | No | No |
| Amazon Cloud Drive | Yes | No | Yes | No |
| Microsoft One Drive | No | Yes | Yes | No |
| Hubic | Yes | Yes | No | No |
| Backblaze B2 | No | Partial | No | No |
| The local filesystem | Yes | Yes | Depends | No |
MD5SUM
The cloud storage system supports MD5SUMs of the objects. This
is used if available when transferring data as an integrity check and
can be specifically used with the --checksum flag in syncs and in
the check command.
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
- 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.