Even using sha-256 or greater type of hashing, I'd still have concerns about letting a system make deletion decisions without my involvement. I've even been part of de-dupe efforts, so maybe my hesitation is just because I wrote some of the code and I know I'm not perfect in my coding or even my algo decision trees. I know that any mistake I made would not be of malice but just ignorance or other stupid mistake.
I've done the entire compare every file via hashing and then log each of the matches for humans to compare, but never has any of that ever been allowed to mv/rm/link -s anything. I feel my imposter syndrome in this regard is not a bad thing.
Now you understand why this app costs more than 2x the price of alternatives such as diskDedupe.
Any halfway-competent developer can write some code that does a SHA256 hash of all your files and uses the Apple filesystem API's to replace duplicates with shared-clones. I know swift, I could probably do it in an hour or two. Should you trust my bodgy quick script? Heck no.
The author - John Siracusa - has been a professional programmer for decades and is an exceedingly meticulous kind of person. I've been listening to the ATP podcast where they've talked about it, and the app has undergone an absolute ton of testing. Look at the guardrails on the FAQ page https://hypercritical.co/hyperspace/ for an example of some of the extra steps the app takes to keep things safe. Plus you can review all the proposed file changes before you touch anything.
You're not paying for the functionality, but rather the care and safety that goes around it. Personally, I would trust this app over just about any other on the mac.
Best course of action is to not trust John, and just wait for a year of the app out the wild, until everyone else trusts John . I have enough hard drive space in the meantime to not rush into trusting John.
Yeah, the lack of involvement was more in response to ZFS doing this not this app. I could have crossed the streams with other threads about ZFS if it's not directly in this thread
I've done the entire compare every file via hashing and then log each of the matches for humans to compare, but never has any of that ever been allowed to mv/rm/link -s anything. I feel my imposter syndrome in this regard is not a bad thing.