71 lines
2.8 KiB
Markdown
71 lines
2.8 KiB
Markdown
---
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title: "Overview of cloud storage systems"
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description: "Overview of cloud storage systems"
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type: page
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date: "2015-09-06"
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---
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# Overview of cloud storage systems #
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Each cloud storage system is slighly different. Rclone attempts to
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provide a unified interface to them, but some underlying differences
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show through.
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## Features ##
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Here is an overview of the major features of each cloud storage system.
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| Name | MD5SUM | ModTime | Case Sensitive | Duplicate Files |
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| ---------------------- |:-------:|:-------:|:--------------:|:---------------:|
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| Google Drive | Yes | Yes | No | Yes |
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| Amazon S3 | Yes | Yes | No | No |
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| Openstack Swift | Yes | Yes | No | No |
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| Dropbox | No | No | Yes | No |
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| Google Cloud Storage | Yes | Yes | No | No |
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| Amazon Cloud Drive | Yes | No | Yes | No |
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| The local filesystem | Yes | Yes | Depends | No |
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### MD5SUM ###
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The cloud storage system supports MD5SUMs of the objects. This
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is used if available when transferring data as an integrity check and
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can be specifically used with the `--checksum` flag in syncs and in
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the `check` command.
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### ModTime ###
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The cloud storage system supports setting modification times on
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objects. If it does then this enables a using the modification times
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as part of the sync. If not then only the size will be checked by
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default, though the MD5SUM can be checked with the `--checksum` flag.
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All cloud storage systems support some kind of date on the object and
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these will be set when transferring from the cloud storage system.
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### Case Sensitive ###
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If a cloud storage systems is case sensitive then it is possible to
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have two files which differ only in case, eg `file.txt` and
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`FILE.txt`. If a cloud storage system is case insensitive then that
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isn't possible.
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This can cause problems when syncing between a case insensitive
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system and a case sensitive system. The symptom of this is that no
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matter how many times you run the sync it never completes fully.
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The local filesystem may or may not be case sensitive depending on OS.
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* Windows - usuall case insensitive
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* OSX - usually case insensitive, though it is possible to format case sensitive
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* Linux - usually case sensitive, but there are case insensitive file systems (eg FAT formatted USB keys)
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Most of the time this doesn't cause any problems as people tend to
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avoid files whose name differs only by case even on case sensitive
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systems.
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### Duplicate files ###
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If a cloud storage system allows duplicate files then it can have two
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objects with the same name.
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This confuses rclone greatly when syncing.
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