Solid

I'm bullish on Solid, and I think GemDrive compliments it nicely. While GemDrive aims to provide the minimal necessary filesystem features, Solid takes a comprehensive top-down approach to providing a personal (and private) storage solution.

The main advantage GemDrive has over Solid is simplicity. Solid requires compliance with various different standards. The package.json file for the community server lists over 50 dependencies. GemDrive is just a minimal JSON layer on HTTP. You don't need client libraries to talk to a server. You don't even need libraries to write a server. The reference server ships as a single static executable. It also currently has 3 dependencies, one of which I wrote primarily for GemDrive.

remoteStorage

remoteStorage is an excellent protocol that is very similar to GemDrive. The differences are mostly in the details.

• GemDrive can be hosted entirely from a static fileserver, by pre-generating the index.
• GemDrive supports server-to-server transfers.
• GemDrive supports modifying files/partial uploads.
• GemDrive specifies a way for the server to provide thumbnails and previews, which is critical for remotely browsing data.
• GemDrive supports hosting web pages as a first-class use case.
• remoteStorage used JSON-LD. GemDrive is simple JSON.
• remoteStorage uses WebFinger.

WebDAV

WebDAV is so close to being what we need, but it's just too complicated.

• A GemDrive server is user software, not system administrator software. Everyone is encouraged to run their own server, or even one on each of their devices.
• GemDrive is generally lower level, with a few notable exceptions such as built-in image resizing.
• In general, while client complexity is on the same order (though GemDrive is still considerably simpler), server complexity for WebDAV is much higher. This makes it more difficult to have competing implementations, and perhaps more importantly makes it difficult to include compatibility in existing software. GemDrive lends itself very well to being tacked on to other servers as a module.
• GemDrive is simpler. It's intended for self-hosters to easily run on their own devices.
• WebDAV uses XML. GemDrive uses simple JSON.
• WebDAV requires special HTTP methods, GemDrive uses only HTTP/1.1 methods.
• WebDAV implementations don't seem to be very compatible with each other.
• WebDAV has a heavy focus on file metadata. GemDrive only provides minimal metadata which is already available from the filesystem. This greatly simplifies the state the server must maintain.
• GemDrive doesn't specify file locking. Something along these lines may be added in the future, depending on real-world needs. So far I haven't needed it. Again, this adds a lot of state to the server.
• GemDrive is designed to be run on a normal filesystem which is probably used by other applications, such as running it on your desktop. This means it must be easy to run (no fancy runtimes or build steps) and forgiving of things such as other programs deleting data.
• GemDrive specifies an auth method that can be shared between implementations.

Amazon S3

• S3 requires a complicated auth implementation which doesn't lend itself to web apps.
• S3 is object storage, and as such can't support partial file writes.
• Protocol itself is clunky.
• Not open source. though there are open source implementations such as minio.

Google Drive

In practice, Google Drive is probably the most successful example of what GemDrive aims to accomplish, which is providing user-controlled filesystem storage for web apps. Many popular apps have added support for Google Drive.

Unfortunately, it has some issues:

• No longer supports hosting websites.
• Has weird limitations that are annoying/impossible to develop around. Note that I believe these mostly exist for security reasons, but I think it's possible to have both security and functionality for cloud storage.
• Not open source/can't self-host.

Dropbox

Dropbox actually provides some really nice libraries for using as a backend for app storage. I'm surprised more developers haven't built their apps against it. There may be limitations I'm not aware of.

These are the ones I do know:

• No longer supports hosting websites.
• Not open source/can't self-host.

SFTP

• SFTP doesn't work in browser apps.

NFS

• NFS doesn't work in browser apps.

FTP

• FTP doesn't work in browser apps.