While it is possible to use to use ZotPad without a file server, using some kind of online file storage is highly recommended. The currently supported file storage services are Zotero file storage, WebDAV, and Dropbox. The table below summarizes the different alternatives and more discussion about the differences is provided below.
|Zotero file storage|
|Dropbox with symbolic link or by setting the Zotero data directory in Dropbox|
|Dropbox with ZotFile|
Zotero file storage and WebDAV are solutions that are directly supported by Zotero and Dropbox based options are more or less third-party solutions. Zotero file storage has several advantages that are not available with other file storage solutions. First, uploading a file from ZotPad involves two actions: uploading the file and registering the new file on the Zotero server. The registration step is needed to let your desktop Zotero know that a new file is available. Zotero file storage combines these two into a single atomic transaction that guarantees that the data on the Zotero server will always match the file stored online. Although it is rare, all the other file storage approaches can result in situations where the file that is stored online is out of sync with the Zotero server leading to potential loss of data or failure to synchronize the edited file back to desktop Zotero. Another advantage of Zotero file storage is the ability to upload only the part of the file that has been modified. For example, if you are annotating a PDF book, partial upload would only upload the modified annotations instead of uploading the entire book with all the texts and images every time you want to upload your changes to the server. If you are working with a slow internet connection, this can be a significant advantage. (Partial uploads will be supported in the 1.3 version of ZotPad.)
The difference between the Dropbox based solutions is that in the symbolic link or data directory solutions all the files stored in Zotero will be synced to the Dropbox cloud, where as in the ZotFile based solution the user must choose to send and get files from the tablet. (This workflow is described on the ZotFile website.) The advantage of using ZotFile is that you can manage how much space you are using on Dropbox. The disadvantage is that this setup requires the most user interaction. In the other three file storage solutions all files are available online all the time and synchronized in the background without user intervention, but with ZotFile the user needs to manage the synchronization manually in Zotero.
Dropbox bases solutions have an additional disadvantage. The desktop version of Dropbox will upload a file as soon as it is modified, but the file is marked as modified on the Zotero server only after Zotero is synchronized the next time. This means that the file storage and Zotero server will be often out of sync for at least short periods of time. The iPad/iPhone version of Dropbox works differently from the desktop version in that new versions of files are not downloaded automatically, but need to be requested. Currently ZotPad uses information from the Zotero server to decide when it needs to download a new version of a file. Because the Zotero server and Dropbox can be out of sync, it is possible that ZotPad does some unnecessary downloads or does not download the most recent version. This is not a major problem because files on ZotPad can be manually refreshed by purging the locally cached copy and down loading a new version from Dropbox.
Which one of these you should use depends on how you use Zotero. Here are some suggestions:
- If your employer pays for your online storage, or cost is not an issue for some other reason, always use Zotero storage.
- If you are only using My Library, use WebDAV. Zotero Wiki provides a list of WebDAV services that are known to work with Zotero.
- If you are a member of a research group, register one additional user account. Purchase additional storage for this account and then use the account to create groups where you invite the members of your research group. Use a free WebDAV service for My Libraries.
- You should not use ZotFile if the total size of your libraries does not exceed the space that you want to use for it in Dropbox.
- Dropbox with symbolic link is almost never the best choice, and storing the entire Zotero data directory in Dropbox is even worse because you risk corrupting your data.
If you would like to have support for some other file storage service, please make a feature request or give a vote on existing request.