We have discussed at some length whether we keep Legacy Sync's single set of synced data types or whether we allow per-device synced data types. With the time crunch to push FxA Sync out the door, I'm going to suggest that we do the simplest thing possible, which on Android is per-device synced data types. What this will look like is that the user makes per-device data type elections at Sync set up time on the device [1] and then the user can toggle each data type using Android's Sync management UI [2]. I want to do this for a bunch of reasons: * data type synchronization across devices is a major headache; it's one of the global race conditions that is known and hard to handle client-side. * on Android, it's a good deal of code to convert Android's Sync management UI into data type synchronization across devices. It's a good deal more testing. * on Android, we already have code to sync only certain data types that's fairly robust and easily applied to this case. * we still have Desktop client bugs that bust the meta/global data type synchronization on an infrequent but regular basis. Now, on Desktop this is not how Legacy Sync works. I suggest we hide completely the option to disable things for FxA Sync, at least at first. This is perhaps not feasible with the current desktop? I don't know. [1] Or the user is driven to sync everything, always, at the very beginning; this will irritate users who don't want something stored on the server at all because there's no way to delete a specific collection on the server. [2] see attached image. I propose to make those checkboxes have local effect only.

Desktop folks: is it too much effort to disable data type selection? Or make it per-device on desktop?

(In reply to Nick Alexander :nalexander from comment #1) > Desktop folks: is it too much effort to disable data type selection? Or > make it per-device on desktop? Nope, it's not difficult to disable. It wouldn't be all that difficult to make it per-device, either (at least in the current prefs system): partly undo Bug 578671, which makes meta/global the arbiter of which engines sync. This will also fix a bunch of bugs!

:rnewman understands this issue better than I do wrt Desktop. Per-device for this effort sounds good to me. We need product and UX input (or least acknowledgement) on this decision.

This is done.

We implemented shared data-type selection, with all of its flaws.