[binbasti]

I didn't notice that JMAP includes calendars and contacts. Looks good!

Personally, I'd prefer a dumb storage with a generic API over yet another custom protocol/API just for these data formats alone. Worked great on people's local drives before the Web, and I think it should work similar on the Web.

[robn_fastmail]

Dumb storage is fine if you only have a single actor that can maintain a copy of the state at all times. As soon as you've got multiple actors on the data (another client on your desktop or phone, or even something doing mail delivery), then you need a way to determine what changed on the server so you can update your state.

If the server has no ability to tell you what changed, then you're left with having to download and check everything. On a large data set, that's pretty much impossible to do quickly and without a lot of network traffic.

Of course, no server is actually that dumb - even a file listing with file sizes can get you part of the way there. But if you've got 10000 files in a file store, that list can still get pretty heavy. If you're willing to make the server smarter, eventually you can get to the point where the server can give you only what changed since the last time you checked. JMAP isn't unique in this; IMAP has MODSEQs, *DAV has collection synchronisation, etc.

JMAP specifically doesn't really care much about the actual format of the data it works with. The only thing it really needs is an immutable ID, so you could use the same model to store all sorts of things (and at FastMail we do, with things like client settings).

[binbasti]

> Of course, no server is actually that dumb - even a file listing with file sizes can get you part of the way there. But if you've got 10000 files in a file store, that list can still get pretty heavy.

Exactly. remoteStorage has ETAGs in folder listings for that. The point is that you can implement a folder structure that enables you to update say just the last week of events plus upcoming ones, which is usually nowhere near 10000. Except with CalDAV you can't (according to the article, I haven't actually looked into it myself).

[untitaker_]

I guess you can dump a [Maildir](http://cr.yp.to/proto/maildir.html) (or at least a modified version) into a remoteStorage, but this is not really an acceptable protocol for mobile clients with limited space. As mentioned in the blogpost I have the same problems with storing calendars in remoteStorage.

[treve]

Except that a dumb storage cannot do scheduling, and many other things.

[binbasti]

The storage can't do the scheduling itself, but apps can do it on top of dumb storages.

[untitaker_]

I guess that's an expendable feature.