# OS Reinstall improved performance



## mcasan (Jul 29, 2019)

It has been many years since I did my first MacOS install. Lots of MacOS versions and photography apps have come and gone. Despite using AppCleaner to “completely” remove all the files an app can litter about in the file system, detritus does pile up in a computer just like in our attics and basements.

So after a Time Machine backup, I used Recovery to reformat my Macintosh HD and then installed Mojave. Since I use iCloud for things like KeyChain, Mail, Safari…all those settings were restored from iCloud once the installation was over. I then downloaded Creative Cloud and had it download Lr Classic and Ps. I told Lr to open the existing catalog which does not reside on the boot SSD. It opened just fine and accessed the various folders of images.

The reinstall seems to have made a noticeable improvement in performance. So if you have not done a complete reinstall in years, and the machine is acting a bit slow…a reinstall _may_ be in order. Of course you must have full system backups before considering a system reload.


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## PhilBurton (Jul 29, 2019)

mcasan said:


> It has been many years since I did my first MacOS install. Lots of MacOS versions and photography apps have come and gone. Despite using AppCleaner to “completely” remove all the files an app can litter about in the file system, detritus does pile up in a computer just like in our attics and basements.
> 
> So after a Time Machine backup, I used Recovery to reformat my Macintosh HD and then installed Mojave. Since I use iCloud for things like KeyChain, Mail, Safari…all those settings were restored from iCloud once the installation was over. I then downloaded Creative Cloud and had it download Lr Classic and Ps. I told Lr to open the existing catalog which does not reside on the boot SSD. It opened just fine and accessed the various folders of images.
> 
> The reinstall seems to have made a noticeable improvement in performance. So if you have not done a complete reinstall in years, and the machine is acting a bit slow…a reinstall _may_ be in order. Of course you must have full system backups before considering a system reload.


Does your system have an SSD for OS, apps, and perhaps the LR Library?  Or spinning HDD?  

If the latter your disk may have been badly "fragmented" by years of adding and deleting files.  Just doing a defragmentation operation on an HDD can sometimes lead to a performance improvement.  This process requires no reformatting, no re-installation, etc  If you have an SSD, you should not do a defragmentation operation.


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## mcasan (Jul 30, 2019)

My iMac has a 512GB SSD.   All my photos, movies, documents...etc all sit on an external 8TB RAID pair that was not reformatted.   Only the internal SSD was reformatted and reloaded with latest Mojave.


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## PhilBurton (Jul 30, 2019)

mcasan said:


> My iMac has a 512GB SSD.   All my photos, movies, documents...etc all sit on an external 8TB RAID pair that was not reformatted.   Only the internal SSD was reformatted and reloaded with latest Mojave.


If you have an SSD, then my comments about defragmentation do not apply.


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## mcasan (Jul 30, 2019)

Fully understood.  I run APFS on the SSD and Journaled on the external drives.


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## clee01l (Jul 30, 2019)

PhilBurton said:


> If you have an SSD, then my comments about defragmentation do not apply.


"a Mac running any version of OS X later than 10.2 generally doesn’t need to be defragmented. The reason for this is that OS X and macOS have their own built-in Apple Mac utilities that clean up fragmented files from the hard drive. Therefore, for most users it eliminates the need to perform a regular defrag."


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