iMac low-level reformat and TM reinstall.... thoughts?

Dave Everhart1 wrote:

It's been a long time since I've had to do anything like this, and things have changed so bear with...

I've a 2017 iMac, Ventura 13.4. 1TB 5400 rpm (I know... what were they thinking?...). Over the past couple of years it's gotten almost painfully slow most of the time; I've seen more beachballs than the Jersey Shore on a midsummers' day. Kinda thinking that a good ol' low-level reformat - the kind that might take a day or so - and a re-install from a TM backup would go a long way towards alleviating most of this. Probably fragmented beyond belief.

Not sure of the proper steps to take, anymore, since it's been so long.

First, make a current TM backup (if you don't already have one). You can then use Disk Utility in macOS Recovery to erase it before restoring the Mac with said backup. See the links below, they've got all the steps you need. Good luck!

1. Back up your Mac with Time Machine - Apple Support
2. Use Disk Utility to erase an Intel-based Mac - Apple Support
3. Restore your Mac from a backup - Apple Support

I doubt erasing and restoring will make your computer any faster. Long sad history in these forums teach that 95%+ of the reports of slow iMacs here involve 21.5-inch iMacs made between 2012 and 2019 with entry-level mechanical hard drives. With their original OS versions, those worked OK but seems to be glacially slow with newer macOS versions. That won't change after a reinstall.

That is not usually an issue with iMac ordered with Apple's optional SSD or Fusion hybrid drive, as long as the latter is heathy.

That is based on history, not data from your computer. If you want a data-driven evaluation in this setting where we can neither see nor touch your computer, please post an EtreCheck report. We can quickly and within the limitations of these forums help you determine what issues are at play without our playing a protracted game of "20 Questions" with you that could go on for days. 

EtreCheck Pro is available here: https://etrecheck.com/index

The free version will do nicely for this purpose, although the app is worthy of our financial support.

We can see hard data about drive performance, software issues and interferences, and RAM usage. Etrecheck is the development of a long-serving and trusted ASC contributor. It is a reporting app, not a "fix-it” app, expressly for displaying information in these forums to help us help you remotely. As it only reports, It is safe and It will not reveal any personal or secure information.

Please see this excellent user tip on how to post long text reports like EtreCheck's into a forum response:

How to use the Add Text Feature When Post… - Apple Community