Clean install to High Sierra saved me 80+ GB space, and drastically decreased wake-from-sleep delay.

[EugW]

Wow. I went from 372 GB on Sierra HFS+ to 286 GB on High Sierra AFPS. That's a total of 86 GB saved on my 2017 i5 SSD iMac.

Now, about 7 GB of that was due to a smaller Applications folder, since I didn't install a bunch of software I didn't need anymore.

However, Most of the rest of that was in the various Library folders:

/Library - 12.2 GB --> 1.6 GB
~/Library (user 1) - 21.7 GB --> 0.3 GB
~/Library (user 2) - 41.2 GB --> 1.0 GB

Total just in the various libraries = 75.1 GB - 2.9 GB = 72.2 GB

----

I hadn't done a clean install in years. It's amazing just how much junk can accumulate in those Library folders, esp. in the user ones which are hidden. It seems the big ones were ~/Library/Application Support and there are folders in there for software I haven't used in 5 years. The biggest single folder was ~/Library/Application Support/Mobile Sync which is the iTunes backup directory. I guess this one will grow over time again, and yes, one would be able to delete those iOS backups via the Manage Storage tab for About This Mac, but at least I've cleaned out the bazillion other unused folders too.

Boot time has decreased from ~23 seconds (on a 1 TB PCIe SSD) to 17 seconds.

But the best is the improvement in wake-from-sleep. In both Sierra and then High Sierra, wake-from-sleep would take 5-7 seconds each time. It was really irritating, especially considering it would be only one second on my clean installed laptops. After the clean install on this 2017 i5 iMac, wake-from-sleep is now also only 1 second. While it's true deleting iOS device backups would have gotten me most of the space back, I don't think it would have decreased my wake-from-sleep times like this.

 

[GuilleA]

That is awesome.
Most of the junk that accumulates over time are caches, so purging them on a weekly or monthly basis really helps in keeping them in check and preventing from ballooning in size.

Simply manually delete the Library/Caches folder for each user or by using a maintenance app, such as Cocktail, Maintenance, Onyx or CleanMyMac will also detect all the cruft and leftovers.

A clean install is by far the best solution if you've been upgrading OSs for a long time.

 

[torana355]

Im a clean instal addict lol. Every 6 months I do a clean install of the current OS, I find it cathartic.

 

[QCassidy352]

Same here, OP. I did a clean install of HS on my 2013 13" MBP this weekend, and I, too, saved a lot of space. Went from about 50 GB free to about 87 free. Maybe 10 of that is due to not reinstalling a few apps, and the rest seems to be the combination of AFS and clearing out old junk in the library. System is also the fastest and most responsive it's felt in years. Totally worth the time it took to clean install.

 

[zipur]

That is awesome.
Most of the junk that accumulates over time are caches, so purging them on a weekly or monthly basis really helps in keeping them in check and preventing from ballooning in size.

Simply manually delete the Library/Caches folder for each user or by using a maintenance app, such as Cocktail, Maintenance, Onyx or CleanMyMac will also detect all the cruft and leftovers.

A clean install is by far the best solution if you've been upgrading OSs for a long time.

--
Any other folder you can share that "Build Up" over time? -- Thanks for the tip. Not everyone knows the ins-an-outs of Apple IOS.

 

[EugW]

My main concern was if I had done my manual data migration properly. I didn't get why there was such a large discrepancy in the total amount of data. The manually copied over folders (like Pictures) were the right size, but yet, I had this huge discrepancy overall. Only after going through various system folders and the hidden folders individually did I discover just how much junk was in there. As mentioned, the bulk of the space savings was from getting rid of iOS backups, but still, there was just a huge number of support folders for a bazillion different applications, some of which hadn't even been on my system for several years.

System was working fine before, but yeah, now it's way more responsive.

BTW, APFS per se didn't actually save any space. Just before this I had done an upgrade from Sierra HFS+ to High Sierra APFS, and the amount of space used was about the same. It was also as slow for stuff like wake-from-sleep despite the OS upgrade. So that's when I decided to the clean install, and I'm so glad I did.

 

[QCassidy352]

BTW, APFS per se didn't actually save any space.

Oh, ok. I thought it was supposed to, but I hadn't done a HS upgrade, so I have no point of comparison.

 

[EugW]

Oh, ok. I thought it was supposed to, but I hadn't done a HS upgrade, so I have no point of comparison.

Where it saves space is file copies. Now on APFS if say I copy a 5 GB disk image to another directory, the amount of space used doesn't change. The two 5 GB files only take up 5 GB total.

However, when you upgrade from Sierra to High Sierra, any existing duplicate files will still be duplicates.

ie.

On HFS+, if you have two identical 5 GB files in two locations, you will use 10 GB. If you upgrade to High Sierra, they will still use 10 GB.

However, if you delete one of them, and then duplicate it again, the two files will only take up 5 GB total.

Also, because of this, such file copies are near instantaneous, because it's not actually duplicating the data. There is actually only one copy, but with pointers to that same data from different locations.

 

[SaSaSushi]

But the best is the improvement in wake-from-sleep. In both Sierra and then High Sierra, wake-from-sleep would take 5-7 seconds each time. It was really irritating, especially considering it would be only one second on my clean installed laptops. After the clean install on this 2017 i5 iMac, wake-from-sleep is now also only 1 second. While it's true deleting iOS device backups would have gotten me most of the space back, I don't think it would have decreased my wake-from-sleep times like this.

Thanks for sharing your experiences and I'm glad to hear the clean install helped you.

I have to say that I last did a clean install in 2006 and have been migrating through iMacs ever since and yet my wake from sleep time is 2 seconds tops, including the time for my Apple Watch to unlock.

 

[EugW]

Thanks for sharing your experiences and I'm glad to hear the clean install helped you.

I have to say that I last did a clean install in 2006 and have been migrating through iMacs ever since and yet my wake from sleep time is 2 seconds tops, including the time for my Apple Watch to unlock.

I wonder what it was that caused the wake from sleep delay. What I didn't mention earlier is that I even tried a clean install and then a migration of data from a cloned backup using Apple's automated method, but that also caused the wake from sleep delay. Behaviour was exactly the same as an upgrade.

Only after I did another clean install and manual transfer of data did the delay go away.

I guess from this experience and your experience is that if you have no issues or delays in Sierra, then after upgrading to High Sierra, you may still have no issues or delays. However, if you have such delays in Sierra, they may persist after upgrading to High Sierra.

 

[TonyC28]

I am considering a clean install to hopefully improve my iMac's performance. Is there a preferred method of doing a clean install? Will I have to manually transfer files after it's done or can I get them from a Time Machine back up?

 

[EugW]

I am considering a clean install to hopefully improve my iMac's performance. Is there a preferred method of doing a clean install? Will I have to manually transfer files after it's done or can I get them from a Time Machine back up?

Dunno about Time Machine. I gave up on it a long time ago because of problems I had with it.

However, when I used Apple's automated migration method from a cloned backup drive, all the junk that was on the backup was restored to my High Sierra install, so it provided no advantage over an upgrade. The same wake-on-sleep delay came back after the restore.

 

[ashleykaryl]

I initially lost about 40 gigs after upgrading to HS. Then I did a clean install and it leapt from 60 gigs to 160 gigs after re-installing all the apps.
[doublepost=1506960778][/doublepost]

I am considering a clean install to hopefully improve my iMac's performance. Is there a preferred method of doing a clean install? Will I have to manually transfer files after it's done or can I get them from a Time Machine back up?

It can be time consuming, but I think the trick is to make good use of iCloud, so everything like bookmarks, keychains and internet accounts just filters back in place afterwards. That way you just re-install the apps you want and drag across any required information from a backup drive.

If you use the migration tool, you basically end up with a clone of what you already have and the aim is to have a clean system where you erase everything and start from scratch. You definitely want your entire system backed up though on a separate drive before starting.

 

[TonyC28]

Dunno about Time Machine. I gave up on it a long time ago because of problems I had with it.

However, when I used Apple's automated migration method from a cloned backup drive, all the junk that was on the backup was restored to my High Sierra install, so it provided no advantage over an upgrade. The same wake-on-sleep delay came back after the restore.

[doublepost=1506960778][/doublepost]

It can be time consuming, but I think the trick is to make good use of iCloud, so everything like bookmarks, keychains and internet accounts just filters back in place afterwards. That way you just re-install the apps you want and drag across any required information from a backup drive.

If you use the migration tool, you basically end up with a clone of what you already have and the aim is to have a clean system where you erase everything and start from scratch. You definitely want your entire system backed up though on a separate drive before starting.

Thank you. Since upgrading to High Sierra my mid-2011 iMac is a little clunky and the Photos app is almost unusable at this point. I'm hoping a fresh install will get it back to performing well even though it's getting a little old.

 

[EugW]

Thank you. Since upgrading to High Sierra my mid-2011 iMac is a little clunky and the Photos app is almost unusable at this point. I'm hoping a fresh install will get it back to performing well even though it's getting a little old.

What's wrong with Photos?

With my clean install of Photos and 235 GB Photos library, it's very fast.

 

[TonyC28]

What's wrong with Photos?

With my clean install of Photos and 235 GB Photos library, it's very fast.

It is terribly slow. I have a pretty small library but everything just moves slow. And editing is a nightmare. Mouse clicks take several seconds to register. Moving sliders or crop windows is delayed by several seconds. It’s almost like something got messed up when I updated.

Update: Just finished a clean install and I still have the problem. As much as I like the new features in Photos it looks like I'll be switching to Lightroom.

 

[ashleykaryl]

I have an old iMac from 2007 that was painfully slow. The latest system it will run is El Capitan, but I did a clean install recently and the performance now is quite acceptable for general usage. On the subject of HS, it's basically running fine for me now and I'm glad to have all that drive space back, but I certainly haven't seen any real performance gains over Sierra. Hopefully these will come after a couple point updates when Apple has worked out the gremlins.

 

[nordique]

I didn't clean install, but did get about 20GB back after installing yesterday. Wow!

Also, it is blazing fast...Mid 2012 MBP (non retina) with ssd hooked up to TB display

Its so fast! I came from El Capitain and am noticing a speed increase!

Only issue for me is when I go to sleep and turn off bluetooth keyboard/mouse, the computer wakes from sleep instantly. Have to to solve that one out but otherwise very happy with High Sierra