Currently re organising my backups and notices a large discrepancy in data on external drives.

2TB external drive says its used 900GB
I used Carbon Copy Cloner to make a backup of that drive to my NAS and it copied 350GB then says complete. When I checked, I can’t see any missing files. It looks like the 2TB external drive is sayings it’s used way more space than it really has. I’ve checked the obvious things like trash etc. But this has me stumped.

Any experience with this kind of thing?

Check what CCC is cloning for you in the advanced settings. You might need to RTM.
The default is user data.
It will not clone your MacOS partition, reinstall partition, Time Machine snapshots, or apps by default.
Also, you can, as far as I know, only make a full boot drive clone to an afps formatted drive these days.

Use Time Machine – so much better than CCC.

I run x2 external hard discs and I rotate them at the end of each week (one comes home with me, one stays at work). But one is always plugged in while I’m working.

It’s saved my arse on numerous occasions! 🙂

CCC is good if you want to make a clone drive, do mine monthly should my SSD fail I can boot to that…..
Otherwise its iCloud and TimeMachine backing up to my NAS.

Versioning?

CCC is good if you want to make a clone drive, do mine monthly should my SSD fail I can boot to that…..
Otherwise its iCloud and TimeMachine backing up to my NAS.

same here. Plus backblaze.

CCC is great for making a clone of your boot drive. And for cloning content from one location to another.

Note that I saw in MacFormat the other month a help question on back ups and CCC, and it was pointed out that cloned boot drives don’t work in Ventura. I think. Not really helping the OP, possibly incorrect info. But, maybe useful.

CCC worked really well, saved me twice over the last 20 years.

I use Time Machine too.

Have the Boot drive and external drive both backed up with TM, though TM keeps getting stuck and taking hours to copy a few hundred MB. Just set up my old Mac as a NAS since it had 4 empty HDDs.

CCC over my home network is much faster than TM so want to use that. Just can’t work out why it’s not cloning everything. Also, rhe external drive is just data, not system files.

Used to use it years ago but CCC is somewhat old hat these days IMO. If I have any kind of drastic failure I’ll just nip out, buy a new Mac, download my files off Backblaze, re-install my apps & be working again quicker than I could figure out why my freshly cloned drive isn’t booting 😀

TM isn’t meant to be quick it just chugs along in the background doing what it does while you work.

If you plug a disc and watch it back-up then yes it will be slow.

I use BackBlaze. 6 macs in our house, all using it.
Sits in the background and just gets on with it. It’ll back up external drives too, and there’s no limit??? All stored off-site with complete restores available from them, inline, or via new, posted drive in a couple of days. Amazing.

Cheaper over the years than buying a new external backup drive every few years and i don’t have to do anything.

First complete backup takes a long time, but then only adds new files etc:

Looks like CCC no longer clones using it’s own software. Apple insist that the process is handled by one of their routines. The software is not supported for cloning but will still do it as a legacy process. Probably explains why it got cheaper with the last update to version 6.