How to safely erase hdd and reinstall?

[0906742]

OK. Thanks. So I settled with encrypted USH hdd/TM backup and it is recommended as to prevent anyone accessing my data in case I lose my USB hdd or someone steal it.

I will later see if I also turn on FIleVault option for internal system SSD. I guess I should do that also and since it should not cause any confusion with the current method I use TM.

EDIT. Seems to take quite a bit longer to do TM backup with encrypting on than it did without it. It has already taken about as long as it did whole backup without encryption but now it is still under 50%... Is that normal?

 

[0906742]

Incredible slow. I just checked activity monitor and it shows disk activity from like 50KB to maybe 20MB at the best. It started much faster but it basically slowed down to crawl in a moment. CPU usage is very low and MacBook fan is not even running (Air 2018). Is it due to encrypting or what (Is Air 2018 cpu so slow it causes this? I though T2 chip should do the work and not cause difference between Air and Pro models with encryption). Before I tried it on this same hdd with original OS installation with 10GB more data and it was completed already while this is still half way. It did then also slow done for quite some time in some point but it did not last this long.

About how long it should take when there is about 21GB data to back up to USB HDD with encryption on with Air 2018? It is WD Elements 2.5" hdd at it was empty and just created partition like I mentioned in previous messages. I'm using Apple original USB C to USB adapter I just bought. Based on BlackMagic speed test it is running about the same speed as directly plugged in my another Windows notebook without USB C adapter in the middle. It was about 125/125MB write/read in Windows machine and in this it give about 110-115/120 write/read in test with encrypted drive. It was bit higher write speed without encryption (maybe a bit over 115, still a bit under what in Windows machine but it was also with different testing program so it might explain the difference too).

 

[Fishrrman]

OP:

I think that you're "thinking way WAY too much".

If you want to "wipe" the hard drive, and start with a completely fresh OS install, just:
- boot to INTERNET recovery (NOT to the recovery partition)
- ERASE the ENTIRE internal drive with Disk Utility (be sure to choose "show all devices" from the popup in the upper left)
- Then open the OS installer and install a fresh system.

Then, either -
- set it up with a NEW user account,
or
- restore your data from a backup.

I NEVER use Time Machine and I ALWAYS recommend that folks use either CarbonCopyCloner or SuperDuper for their backups -- but that's just me, and I'll never change from that, regardless of what others say.

 

[Weaselboy]

That first TM backup is usually pretty slow... just let it run and finish and subsequent incremental backups will be much faster.

 

[0906742]

Thanks again for your advice.

OP:

I think that you're "thinking way WAY too much".

I know, I'm guilty for that. I always tend to prepare for the worst possible outcome...

If you want to "wipe" the hard drive, and start with a completely fresh OS install, just:
- boot to INTERNET recovery (NOT to the recovery partition)
- ERASE the ENTIRE internal drive with Disk Utility (be sure to choose "show all devices" from the popup in the upper left)
- Then open the OS installer and install a fresh system.

Then, either -
- set it up with a NEW user account,

These steps are exactly what I did. I mean I don't know how to tell it is doing internet recovery but I guess it must have since I wiped HDD, so it could not come from there, unless it keeps hidden partition there even you wipe the whole disk.

I NEVER use Time Machine and I ALWAYS recommend that folks use either CarbonCopyCloner or SuperDuper for their backups -- but that's just me, and I'll never change from that, regardless of what others say.

That's exactly what I do with Windows machines always. I never use any os backup or restore tools but some known disk imaging tools (Macrium Reflect Free is my favourite). I need to check those you mentioned also. Is there some fully functional demo or free versions or just full pay versions? I guess I could use them along with TM. I'm so new to Mac OS I'm relying on these OS build in newbie tools for now.

That first TM backup is usually pretty slow... just let it run and finish and subsequent incremental backups will be much faster.

Yeah, I know it takes longer first time but I tried it with original OS to the same hdd but it was not encrypted then and it took about 50 minutes. Now with encryption on it took about 90 minutes with even less data than in earlier test. Does encryption really slow it so much? I don't think CPU power was cause for slowness because fan was not even running and when I checked CPU resources during backup it was very low usage (well under 20% total load). Not sure what gives? Is T2 chip the problem or drive itself (I don't believe it is the drive since it worked fast without encryption).

 

[0906742]

I get the feeling all this was a side point: The main point is you did all this because you're having an issue with your GPU and you were hoping a clean install would fix it, but it didn't. I'd consider making a genius bar appointment. I'm quick to point out Apple's faults, but the quality of their screens has always been top notch. If you see a noticeable visual issue, it's worth checking for a GPU problem.

I think I have found part solution to this but I'm still wondering if it should be like that. I posted more information about my latest finding and there is also my original message with photos and description about this problem. Do you think that is normal what I'm experiencing with my Air 2018?

2018 Air Screen + 10.14.5

 

[0906742]

That first TM backup is usually pretty slow... just let it run and finish and subsequent incremental backups will be much faster.

Yeah, I know it takes longer first time but I tried it with original OS to the same hdd but it was not encrypted then and it took about 50 minutes. Now with encryption on it took about 90 minutes with even less data than in earlier test. Does encryption really slow it so much? I don't think CPU power was cause for slowness because fan was not even running and when I checked CPU resources during backup it was very low usage (well under 20% total load). Not sure what gives? Is T2 chip the problem or drive itself (I don't believe it is the drive since it worked fast without encryption).

I upgraded from Air 2018 to entry MBP 2019 model and I set it up as new machine etc. and then I also formatted external USB HDD I used with my Air for Time Machine backups. Interestingly MBP did the the first full encrypted TM backup in about 30 minutes. Incredible speed difference since Air took about 90 minutes. 3x faster in MBP.

By the way, I recently got Samsung T5 USB-C SSD drive and started to use it as a TM backup drive. It was interesting that USB SSD did not much improve TM full backup time. It was maybe 10% faster (took about 27 minutes) than to USB HDD.

 

[0906742]

How to free HDD/SSD space in Mojave after installing OS update? I just did 10.14.5 to 10.14.6 update and I noticed that free space in SSD decreased almost 10GB. I also noticed that in disk utility where is shows free, for example in mine currently free 94,85GB (17,25GB purgeable) but I find no place where to select to purge right away.

Before last update purgeable space also reported much lower, so obviously it is holding old OS version files somewhere.

I guess that purgeable space is automatically freed if I would start filling up the disk?
Is there an easy way to purge them right away?

 

[Weaselboy]

It is probably just Time Machine local snapshots that will go away in 24 hours. Or you can run this in Terminal to erase them now.

tmutil  listlocalsnapshotdates / |grep 20|while read f; do tmutil deletelocalsnapshots $f; done

 

[0906742]

OK. I will try that. Is there any side effects from deleting them like that?
Do it also automatically delete them right away if I make TM backup again?

I have TM setting normally so that it will not automatically backup (I always initiate it myself).

 

[Weaselboy]

It won't hurt anything to erase them manually. The system will purge them in 24 hours anyway.

 

[0906742]

OK That is good to know. I thought TM would not do anything if I uncheck backup automatically option, but obviously it is doing something in the background despite of that.

I have had earlier like 3-5GB purgeable space but when I ran TM manually that did not change, nor it changed after few days, it just increased gradually little by little every day. Until now OS update +10GB right away.

 

[0906742]

It is probably just Time Machine local snapshots that will go away in 24 hours. Or you can run this in Terminal to erase them now.

tmutil  listlocalsnapshotdates / |grep 20|while read f; do tmutil deletelocalsnapshots $f; done

Thanks! This did the trick and removed that over 10GB that came after OS update to latest version and free disk space is now even slightly more than it was before update.

I'm still wondering what else purgeable files there are since disk utility still shows almost 5GB purgeable. That is something that has been increasing a bit by bit in couple weeks of use. I haven't dowloaded anything on iTunes and I have removed temporary internet history etc... usual suspects.

 

[Weaselboy]

I'm still wondering what else purgeable files there are since disk utility still shows almost 5GB purgeable.

Probably just some misc. cache files.

You can run this in Terminal and it will list all the base folder and their size. That will sometimes show if things look off.

sudo du -d 1 -x -c -g /