Deleted photos, accounts, etc are definitely deleted and purged from our systems.
We have teams at Google whose sole purpose is to ensure that data that should be deleted is deleted in a timely manner (as defined by TOS and the law).
Basically, every piece of user data that is stored at Google has to have a documented and audited retention plan that covers how it is stored, how long it is retained, how it can be used, etc. The retention plans are reviewed by legal counsel and are audited by independent teams.
From a technical standpoint, Photos doesn't deal directly with individual machines or hard drives. There are several layers of abstraction to map what we think of as a "file" and the storage system are doing something that is _effectively_ at least a defrag on a regular basis.
[I work on Google Photos and used to work on storage infrastructure]
We have teams at Google whose sole purpose is to ensure that data that should be deleted is deleted in a timely manner (as defined by TOS and the law).
Basically, every piece of user data that is stored at Google has to have a documented and audited retention plan that covers how it is stored, how long it is retained, how it can be used, etc. The retention plans are reviewed by legal counsel and are audited by independent teams.
From a technical standpoint, Photos doesn't deal directly with individual machines or hard drives. There are several layers of abstraction to map what we think of as a "file" and the storage system are doing something that is _effectively_ at least a defrag on a regular basis.
[I work on Google Photos and used to work on storage infrastructure]