Very Slow Time Machine Backups

swiftaw

macrumors 603
Original poster
Jan 31, 2005
6,309
20
Omaha, NE, USA
Is anyone else having an issue in Mojave where it seems that Time Machine backups are really slow. For example, it is taking 20 minutes to back up about 300MB.

It is backing up to a Time Capsule connected by Ethernet.
 
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kohlson

macrumors 68020
Apr 23, 2010
2,034
548
Is this the first backup? That can be slow. 300GB is a lot of data. Even now, My TC backups of 5-15GB can take a few hours.
 

sracer

macrumors G3
Apr 9, 2010
8,400
8,794
Prescott Valley, AZ
Is anyone else having an issue in Mojave where it seems that Time Machine backups are really slow. For example, it is taking 20 minutes to back up about 300MB.

It is backing up to a Time Capsule connected by Ethernet.
How old is the drive being used to contain the backup? Is it possible that the drive is in the process of failing?
 
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dirt farmer

macrumors 6502
Feb 23, 2005
392
10
Did you make any small, seemingly insignificant changes? One time all I did was select all 10,000 of my iTunes songs and deleted the "genre" fields. Seemingly insignificant. But my next backup took over an hour, just because of that.
 
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treekram

macrumors 68000
Nov 9, 2015
1,849
401
Honolulu HI
Sometimes it takes a long time if it has to prune old backups.
Exactly - check to see if the backup disk is close to being full - if it had to prune, it will typically prune more than what is necessary to fit your newest backup. This pruning operation can take some time to do. If your backup disk is near full, then future backups will also take longer to do as pruning takes place and the only way to speed that up is to 1) delete older backups when you have the time; 2) get a larger backup disk and transfer your backup to the disk; 3) replace the backup disk with a new one - you have to do a full backup to the new and keep your current backup disk as an archive.
 

Howard2k

macrumors 68030
Mar 10, 2016
2,740
1,984
The speeds are certainly inconsistent and will vary based on file size.

You say that you're using Time Capsule via Ethernet. If you copy a 1GB file between the Time Capsule and your Mac, how long does that take?
 
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Honza1

macrumors 6502
Nov 30, 2013
437
145
US
Speed was probably never top design priority. Top priority was space efficiency and therefore all the file linking... and they succeeded! Since assumption was likely, that the TM disk is always connected, and backup process is running in background, low impact on user use was also critical. So speed was secondary or even lower priority. Pruning the backups often takes long time. Note - pruning is done on disks always - even when they are not full. But when they are full much larger amount of data needs to be deleted which can take long time. Anything with TM disks takes forever- First aid on such disk can take days to run. It is awful number of links to check...
 

Steve121178

macrumors 603
Apr 13, 2010
5,018
4,056
Bedfordshire, UK
I've noticed Time Machine backup performance issues with the last two versions of macOS, although it's most noticeable with Mojave. I'm using the 2TB Apple Time Capsule. I even created backups from new & didn't make any difference. Backups are completing so it's not a major issue, It's just annoying when it's taking so long to backup small amounts of data.
 

Fishrrman

macrumors P6
Feb 20, 2009
17,481
5,677
The broken record:
Try something else, such as CarbonCopyCloner or SuperDuper.

When I back up my "main" partition to an external USB3 SSD using CCC, it takes a boring EIGHT SECONDS to complete the incremental clone...
 
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