⚡️Turbo Tips

I’ve been asked a lot of times about when Smart Update becomes ⚡️Turbo Smart Update, and where the setting is in SuperDuper.

The answer is: there’s no setting. When possible, SuperDuper automatically does a ⚡️Turbo Smart Update.

So, why doesn’t it always ⚡️Turbo?

The rules of the game

Here’s the deal: ⚡️Turbo depends on a number of factors, and you can improve the likelihood it will happen by using a separate Copy Job for each source/destination pair. SuperDuper needs to maintain a relationship between the source, destination, copy method, etc., to ensure that ⚡️Turbo is reliable.

If you change the copy method or the rules, then the relationship between the last backup and the next one has changed…and ⚡️Turbo is disallowed (until the next run).

Turbo also won’t run after a One Time macOS Update, or an Erase, then copy until the second Smart Update.

System effects

SuperDuper also relies on the system’s own mechanism for tracking changes.¹

Many (many) years ago, there was a program that I think was called Synk. It installed a kernel extension that tracked all file system changes and wrote a database into user space that the copy program used to make “smarter” copies.

I remember thinking that was incredibly dangerous at the time. You could change the volume when Synk wasn’t running, or on another system, and Synk would be none the wiser. So, while clever, it wasn’t a reliable method of doing this.

Years later, Apple added fsevents, a system-supported way of doing the same kind of thing. I evaluated it when it was introduced, and it was just too flaky to rely on…it wasn’t worth the risk.

Since then, Apple has made changes to fsevents, making it far more reliable as a source of “truth” about volume status.

Now, it’s no panacea. fsevents doesn’t tell you a ton, and it consolidates its change sets pretty regularly, so it’s not like you can just say “here’s what happened” and replay a bunch of events on the copy and get a good result.

But, as a way of “thinning” the number of files and folders you have to visit, when used intelligently, it works well.

Unless/Until it doesn’t.

Sorry, Charlie

Unfortunately, sometimes fsevents can’t keep up with the number of changes being made to a volume, or needs to flush its internal change database. So even though SuperDuper knows what to do, fsevents can veto our attempt annd say that it has, basically, lost the history—and a full scan is needed.

This can also happen when a drive disconnects unexpectedly, or is unplugged without fully ejecting it.

And, of course, it’s erased when you erase.

Faster, Pussycat! Kill! Kill!

So there you go: ⚡️Turbo Smart Update works on the second and subsequent runs of the same job, when the job itself hasn’t changed in a way that invalidates ⚡️Turbo…as long as the system doesn’t invalidate its change database for the volumes involved.

In the event a full scan is necessary, SuperDuper uses regular Smart Update. And since that’s more than twice as fast as before, it’s less painful than it could be.