If you rely on the seamless sync between Google Photos and Drive, you've probably heard the bad news. After being rumored for a month, the dissociation between the two services was made official in June, and today is the day it happens. From now on, you'll have to figure out a different way to keep your photo gallery and photo files in sync. Sadly, there's no real alternative.
The changes happening boil down to this: from now on, media you upload to Drive won't show up in Photos, and vice-versa. You'll need to move things between the two manually. Even then, changes made on one service won't be reflected on the other, so if you edit or delete an image on Drive, you won't see the same result in Photos. And most importantly, storage space usage will count double for media uploaded in Original Quality.
Google is offering two minor solaces. First is Drive's desktop app, Backup & Sync, where you can choose to upload newly added photos and videos to Google Photos (in the app's preferences). In that case, the uploaded pic gets sent to both services and doesn't take up double the storage, but each instance remains separate so edits and deletes don't get mirrored.
Second is a new option in Google Photos' web interface that lets you choose pics from Google Drive to send to Photos. You'll find it on photos.google.com when you click on Upload, then Google Drive. The option isn't live yet for me, but it should be soon.
If you don't want to use a desktop app or manually back up your photos to Drive too, you can resort to third-party options. For example, we reviewed AutoSync for Google Drive, which lets you pair a folder on your phone with Google Drive and set up two-way sync. Along with Photos' built-in backup, you'll have a way to make sure your media is on both services. Still, you'll be using double the bandwidth and battery life to upload each photo twice, and the pics stored on Drive will count against your storage.
Putting all these alternatives together doesn't begin to replace the existing Drive-Photos sync. It's not a feature I used, but a lot of people relied on it to immediately sync their photos to all their computers, and they're left with half-baked solutions. Our own Artem has voiced his frustration about this to David Lieb, Photos' Product Lead, and we're hoping the complaint didn't land on deaf ears.