Slow backups w/Time Machine and an External HD

Every Monday, I backup my MBP to an external hard drive using time machine. It’s this Lacie HD and I’m using “Mac OS Extended (Case-sensitive, Journaled)” if that matters.

There has got to be a better way. It’s Tuesday and I’m writing this message because it never backed up yesterday. It “prepares” forever and then backing up takes forever, too.

Should I use different backup software? Get a better/faster HD?

Please help! Thank you.

The first snapshot is the worst since the whole thing is being saved and not just the files that were recently changed. Afterward, it should get a bit faster.

So, if this is the first, you could try this:

sudo sysctl debug.lowpri_throttle_enabled=0

This will allow more resources to be used in the backup process. After it is done, it is a good idea to re-enable it:

sudo sysctl debug.lowpri_throttle_enabled=1

Over here I have been using Arq 5 without any problems for a while now. I use it with an external SSD and with Dropbox. Most of my work (including my Tinderbox projects :slight_smile: ) also gets pushed into private Github repositories so I can always accurately rewind them if something goes wrong without ever having to deal with backup software.

A couple of things concern me.

Backing up once a week

I assume you have another online backup such as Backblaze that runs continuously? A week seems like a lot of work to potentially lose.

Case-sensitive file system

My understanding is this can break software when used on your internal drive (where the operating system lives). I don’t know the effect on an external drive, but would check into it.

my strategy

If personally use Carbon Copy Cloner for my weekly backup.
I also have Arq 5 running which does hourly backups to my NAS and an external drive.
Every month I use ChronoSync and backup to one of two drives that I alternate.
And I have Backblaze running continuously.

I find Arq and Backblaze are my go-tos for when I need to recover a file.

I should have mentioned, I do this already! Also, this isn’t the first back-up, it’s the gazzillionth (approximately).

I don’t, but everything (except DT3 dbs and Apps/prefs) are on iCloud.


Maybe I’ll try this.

This sounds complicated and expensive. True or false?

Similar to @JohnAtl I use CCC for most of my backup tasks. I do have Time Machine going to one drive but my daily clone to a SSD is my primary recovery tool.

Cloud storage doesn’t protect against stupid user tricks like overwriting a file or deleting the wrong one. That’s why I have local backups of everything stored in the cloud.

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Time Machine is designed to work with a drive that is connected continuously (or frequently, like daily). Connecting just once a week may be part of the issue. It’s not just copying files — there’s a lot more to it, and I’ve seen the “preparing” step take hours. In the past, this seemed to be more likely to happen when the Time Machine disk was getting full. (This is my experience only, and it hasn’t happened in years.)

That said, I’ve also seen Time Machine get stuck on “preparing” because the backup became corrupted. In that case, the only solution is to wipe out that backup and begin again. Not a great solution. I’ve experienced this twice, but it hasn’t happened to me in 4-5 years. I hope that means Time Machine has become more stable!

If you’re not going to keep a TimeMachine drive connected continuously/frequently, I recommend looking at a different backup solution. Continuous backup is much safer than periodic, but a periodic backup in addition to continuous is a good idea. I use Backblaze (and TimeMachine) for continuous and Carbon Copy Cloner for periodic backups.

Storing everything in the cloud is not a backup. Sync is not backup. If you mistakenly delete (or software corrupts) a file, sync will repeat that error everywhere, and there’s no (easy) way to recover a previously-synced version.

I agree on the case-sensitive being a red flag, but Apple does say it’s OK:

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This is a very helpful reply, thank you!

Your replies have convinced me that we should have something networked and daily. (Honestly, I thought NAS was a brand until now). There’s so much to learn and I don’t have time for this! Any pointers to help me understand where to begin with meeting my needs (which I think are fairly small – one home, two MBPs w/2TBs of storage each)?

I think Backblaze and Carbon Copy Cloner (CCC) would be much less demanding of your time.

The NAS is something you “administer,” not very appliance-like in my experience. (I have a Synology DS918+ $550+4x$120 for drives =~$1k). Admittedly, some of mine could be self-inflicted by learning it’s capable of something, then working to implement that. If I had it to do over, I would probably get a Mac Mini and a couple of external drives. Other people with differing opinions will probably chime in and tell you how super easy it is, and that there are cheaper options, as is their right.

For Backblaze, I’m backing up my M1 MBP and my iMac Pro, I also pay extra for the 1-year data retention, total per year is $168. While I’m a student and make a pittance, I consider $168 to be worth about 2 hours of my time.

CCC is $40.

External 4T drives are about $110.


I think you’re right! Looking into Backblaze and CCC rn, thanks all!


Time Machine seems to be in need of some serious love and attention by Apple. Over the past couple of years it has become horribly slow and unreliable when used over a network - and for anyone with a laptop that’s how one would want to use it! I’ve been backing up MacBooks to networked drives for years now - first using a Synology NAS, and then to external drives on a networked Mac Mini, and it used to be an easy, reliable, set-and-forget, option. However, since Catalina and Big Sur it has become a recurring nightmare, with backups taking hours, even days, and then anyway failing before completion. My M1 MBA has not managed successfully tp complete a TM backup in several weeks! One problem has been that the system seems no longer to be able to deal with a laptop going to sleep, which is a rather fundamental failing!

Of course, the drives to be backed up have been growing, but I don’t believe that can possibly account for the increasing times taken to complete TM backups. Rather, I suspect that this problem has been generated in code changes required by the adoption of the APFS file system. But whatever the cause, Apple need to take a serious look at TM, which as currently implemented seems no longer to be a viable backup system for laptop computers.


At my previous company we used Time Machine over the network but found backups would become corrupt after 4 to 6 months. Eventually we stopped using it around 2016 - 2017.

After I installed Big Sur I did try Time Machine on a locally attached APFS formatted drive. Backups were fast and everything seemed OK for the first couple of weeks. I did a successful test restore after the first complete backup, but when I tried again a couple of weeks later the backups could not be read. I ended up formatting the drive and replacing Time Machine with ChronoSync.


This has been my experience with TM, even with directly-connected drives.
I just don’t trust it anymore. I still like the whole Time Machine paradigm, but as @baldbeardie said, TM needs some attention (as does Apple Mail).


Issues with Time Machine slowness have gone away since I used the Time Machine Editor app to increase my backup interval from the default one hour to three hours between backup attempts (YMMV). To get through your first Time Machine backup, turn off automatic backups and start one manually when you can leave it running all night undisturbed.

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I have been running Time Machine over wifi to back up my MacBook Pro to a shared drive attached to an always on Mac. I am trying to get the benefit of automatic backups without having to plug in an external drive since I use my laptop all over the house (I also use Backblaze so I am not concerned about full data loss), but it’s absolutely brutal. Backups take forever, run past the advertised amount of data to backup, always cleaning up or verifying, and makes the fans scream. It’s a joke.

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During the time we were using TM over the network, I used a Mac mini dedicated to backing up only one senior executive and, as I recall, 4 Drobo 5Ns. Each Drobo had 4 or fewer clients and all devices were on a wired 1gb connection.

Sometimes the Macs would just stop backing up requiring me to remove and re-setup the connection to the destination device. When the volume assigned to the Mac became full TM would not automatically remove the older backups. This occurred on both the Mac mini server and the Drobos. When this happened I would create a new backup volume for the client, then delete the old backup volume after the initial backup on the new volume had completed. But the final straw was the TM backups would eventually become unreadable.

At this point our managers were told we would no longer be backing up their Macs and they should keep both their company data and any personal files in their private directories on a file server. (The majority of our employees used only email and web based applications and didn’t require backups). Eventually we moved to a cloud based backup system.

Have you looked at ChronoSync? This app combined with their ChronoSync Agent, which would run on your always on Mac, was the immediate solution I used to replace TM for our senior executive. It was extremely reliable.


Thanks for the suggestion @WayneG. What I most like about Time Machine is the ability to browse history by date to access previous versions of files and deleted files. It looks like ChronoSync’s solution to this is their Archive feature. Is that right? Do you experience with how using ChronoSync for this would differ from Time Machine? Thanks!

Correct. To restore a file you can use the Archive panel in Chronosync or browse/search the archive folder the same as any other. You can customize what is archived, how many versions to keep, and for how long.

I purchased my personal copy of CS in March 2007 and later purchased multiple copies for my company. It is rock solid and you get free upgrades for life.

Both Chronosync and Chronosync agent are free to use for 15 days.

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Hi Beck.

I have been talking to Apple support over the problem of slow Time Machine backups, which first appeared with Catalina, and has continued into Big Sur.

I was trying to backup a new M1 MacBook Air with about 350GB of data on the SSD. The backup disk was an external drive on a Mac Mini.

Like you, I thought that the backup had frozen, but if I let it continue, it did complete - although it took a long time: just under 30 hours! Subsequent backups were taking maye 7 or 8 hours - and of course, on a laptop this means that backups simply were not completing.

The first thing that Apple told me is is that I should make sure the backup disk is formatted in APFS, Having done this (and I had some initial trouble getting Time Machine to recognise the disk, but resolved that eventually by rebooting the laptop!) the time for the first backup dropped significantly - to about 11 hours, and subsequent backups now take about 2-3 hours. Using a wired connection to the Mac Mini did reduce the backup times, but not by very much. By contrast, using a directly connected drive the first backup takes about 3 hours, and subsequent backups a few minutes.

I am still not happy with backup times, but using APFS for the backup drive are certainly significantly improves things compared to using traditional MacOS formatting. So far as I am concerned this is still an open and on-going support situation.