Time Machine backup larger than my HDD?

iAlexG

macrumors 6502a
Original poster
Jun 15, 2009
509
1
UK
I deleted my Time Machine backup and started again. But when I selected the newly blank drive to backup on i was told 504GB's was needed for the backup and i only had 495 free (Iomega 500GB HD). But my MBP's HDD is 500GB and has like 100GB's free? Whats this 104GB extra?
 

diazj3

macrumors 6502a
Jan 19, 2008
879
135
weird... I assume you have emptied your trash bin, and erased the external drive (using disk utility)...

have you tried using Whatsize or OmniDiskSweeper to find any hidden big files in your computer and/or the external drive?

other than that, I can't think of something else...

good luck
 

iAlexG

macrumors 6502a
Original poster
Jun 15, 2009
509
1
UK
Yep I empty my trash everyday or so and i erased using Disk Utility. I'll try looking for big files later. Thanks
 

dbmnk

macrumors member
Nov 6, 2009
43
0
I have the same problem, only my hdd is only 160 GB, but Time Machine tells my I need some 400 GB on my backup disk, and that my Total Included backup will be 378.1 GB.

Like you I did the Disk utility erase of my backup disk in order to accomodate the problem when first encountered due to some structural changes on my mac hdd. I have emptied the bin and done a restart.
 

Flynnstone

macrumors 65816
Feb 25, 2003
1,423
74
Cold beer land
Time Machine backup drive should be about twice the size of the drive you're backing up. Rough rule of thumb.

Since you're closer to 1 to 1 data size to backup drive size, perhaps SuperDuper or CCC are a better option.
Just my $0.02
 

dbmnk

macrumors member
Nov 6, 2009
43
0
Time Machine backup drive should be about twice the size of the drive you're backing up. Rough rule of thumb.

Since you're closer to 1 to 1 data size to backup drive size, perhaps SuperDuper or CCC are a better option.
Just my $0.02
Thanks, my mac has 160GB and my backupdrive the same. This has worked flawless for years until now after I changed my mac hdd partitition from two to one.

I'd prefer if I could just continue using the same backupdrive, aint there some sort of way to reset timemachine so I could backup from scratch?

Should be noted I have filevault turned on, and apparently filevault only protects the home folder and not additional partititions - hence I collected all my files in the home-folder. Perhaps filevault protected files require double the backup-space?
 

dbmnk

macrumors member
Nov 6, 2009
43
0
Ok, I better clarify:

Before:
TimeMachine works great.

Conditions:
160 GB Mac HDD, 160 GB Backup drive.
Filevault turned on.
Mac HDD in two partititions; Home ~60GB, Media ~100GB, both partititions ~80% full.
Noticed TimeMachine said that the "Total Included" backup size exceeded my Mac HDD size, but didn't react since everything seemed to work fine.


Realized the Media wasn't protected by filevault (apparently), so collected the partititions in one now Home


Now:
TimeMachine refuses to backup, but seems to be willing to backup when logging out, but I cannot access the backup when logged in.

Conditions:
160 GB Mac HDD, 160 GB Backup drive.
Filevault turned on.
Mac HDD in one partitition; Home.
HDD ~80% full.
"Total Included" backup size: 375GB
 

BLBL

macrumors 6502a
Apr 11, 2018
844
125
I would be appreciated if someone with more experience with Time Machine would answer to my newbie question about TM backup HDD size requirements.

My machine is MBP with only 128GB SSD.
I have 1TB USB HDD for TM but I recently purchased Samsung T5 512GB USB-C SSD drive and I want to move that old USB HDD for use in other purposes and take a small partition from my new T5 for TM. I already created 120GB partition to T5 and made full TM backup to it. My MBP SSD is currently only about 25% full and eventually maybe up to 75% wlll be used.

I just read some information telling that backup HDD partition size for TM should be _many_ times larger than MBP internal SSD. Why?
I realize it will be filled from incremental backups but doesn't it delete older backups automatically when more space is needed? Will I run in to troubles with having only 120GB TM backup partition for 128GB MBP internal SSD?

I rather would not sacrifice more space from my USB-C SSD since I'm planning to use rest space for my larger files and possible programs I rarely use with my MBP.

Thanks for everyone bothering to comment on that!
 

BLBL

macrumors 6502a
Apr 11, 2018
844
125
So TM really cannot work with about the same (or slightly) smaller partition size as internal SSD is? It does not automatically delete old incremental backups to make room for new ones?

So I would need to sacrifice whole T5 512GB for TM? Really? If so I guess not point for having SSD for TM backups at all.
 

theluggage

macrumors 601
Jul 29, 2011
4,545
3,340
So TM really cannot work with about the same (or slightly) smaller partition size as internal SSD is? It does not automatically delete old incremental backups to make room for new ones?
So I would need to sacrifice whole T5 512GB for TM? Really? If so I guess not point for having SSD for TM backups at all.
A major point of TM is that it stores the 'history' of files so you can step back to old versions, not just the last version you backed up. There's not much point in using it unless the backup drive is significantly larger than the source drive.

If you don't need that feature and a periodic snapshot of the latest versions of your files is enough, then using something like SuperDuper (CarbonCopy CLoner is the other one) to do periodic 'smart' (incremental) backups is probably more efficient.

In an ideal world, you'd do both as the two methods have different strengths and weaknesses - Time Machine for 'Whups I didn't mean to delete/modify that file just now" and incremental backups for "Whups my SSD just died in the middle of a TM backup...".
 
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BLBL

macrumors 6502a
Apr 11, 2018
844
125
I see this file history is probably desired feature for many peoples but I'm happy with just full backup of my system I make at times when I see fit. So is it so that if I insist using only 120GB partition in my USB-C SSD drive for my 128GB system drive it will stop working when that 120GB partition in USB-C SSD gets full? I does not automatically delete old backups to make room for new ones? Really?

Even currently I use Time Machine setting so that it will not automatically back up anything, I initiate it manually when I want to do it.

I guess I could just sacrifice that old USB HDD with traditional spinning drive just for TM but that just seems a big waste and I would have had better use for that drive in mind if I'm able to use my new USB-C SSD with just 120GB reserved for TM partition...
 

HDFan

macrumors 68020
Jun 30, 2007
2,136
536
recently purchased Samsung T5 512GB USB-C SSD drive and I want to move that old USB HDD for use in other purposes and take a small partition from my new T5 for TM. I already created 120GB partition to T5 and made full TM backup to it. My MBP SSD is currently only about 25% full and eventually maybe up to 75% wlll be used.
Using an SSD for TM is a waste of money. You don't need that speed once the 1st backup is made.

I just read some information telling that backup HDD partition size for TM should be _many_ times larger than MBP internal SSD. Why?
I realize it will be filled from incremental backups but doesn't it delete older backups automatically when more space is needed? Will I run in to troubles with having only 120GB TM backup partition for 128GB MBP internal SSD?
The backup drive is too small, as was mentioned earlier. Spend $40 and get a 750GB portable drive for backups.
Unless you have at least 20% free space on a hard disk you can face performance issues. I just ran a provisioning test on an SSD and the recommended free space was 30%.

You can get a 5 TB hard disk from Costco in the U.S. for $90, 2 TB for $70. Don't try try to shoehorn a TM backup. If you absolutely must shoehorn use something like CC cloner, but you will lose TM's older backup features.
 

mpainesyd

macrumors 6502a
Nov 29, 2008
639
154
Sydney, Australia
Don't skimp on disk space for TM. I agree there is little point in using SSD, unless you need portability.
A big advantage of TM is that it automatically handles more than one backup drive, alternating backups between them. These can have different capacities so I use 500Mb SSD drive for travelling and a 1Tb hard drive for local with my Macbook and use them both while local. By now the SSD drive has fewer historical backups.
 

BLBL

macrumors 6502a
Apr 11, 2018
844
125
Yeah, I guess SSD for TM only would pointless, I was just trying to accomplish my needs for MBP with one external SSD (just give small own partition for TM and other for my data and programs) and use that old USB HDD for something else.

If I insist using TM in small partition, what happens when partition is filled up? Does it automatically remove old backups to make room for new ones, or does it keep asking for more free space?
I don't really need file history and such, just make manually complete backup every now and then and also be able to use that like iTunes backup for IOS devices, so that when you purchase a new machine, you can upload your setting and data easily. This is not possible with TM?

I rather not go buy additional software, and as far as I know CC like programs do not allow to put image on different machine? At least in Windows world those full images are more or less machine specific (basically you could drop it to identical machine easily (and to others by using all kinds of tricks)) but still need to reactivate OS (which is not even allowed or possible in many cases, depending on your licence type) and programs that are depending on machine specific registration).

So I'm interested in using TM in a similar way as iTunes for IOS. Is it possible?
 

mpainesyd

macrumors 6502a
Nov 29, 2008
639
154
Sydney, Australia
As far as I can tell TM automatically deletes "old" files when the destination disk is full. It must be doing that on my SSD because the backup folder is smaller than the backup folder on the HD. So TM seems to manage files according to the space available.
On several occasions I have used a TM backup to set up a new Mac using the Migration function.
 

BLBL

macrumors 6502a
Apr 11, 2018
844
125
This was exactly what I was asking about and sounds like it is doable with TM after all.
I just need possibility to restore my machine as it was in case it needs to be replaced or I buy a new unit, or due to some other disaster I have to format MBP internal SSD. Just like how you can use iTunes for IOS devices to restore them.

So basically I should be all right using only 120GB partition on my external SSD for backing up my MBP 128GB internal os drive (I'm not planning to use internal hdd full capacity anyway, probably under 75% in worst case)?
 

haravikk

macrumors 65816
May 1, 2005
1,494
19
When backing up, Time Machine allows a certain amount of "padding" (extra space) for the backup to try to keep things running smoothly; this helps to ensure there's plenty of working room, and also improve the drive's performance (HFS+ can perform very poorly if it becomes fragmented with less than 10% space remaining).

Time Machine also seems to over-estimate the size of its backups; during backup it may discover duplicate files and other things that can be optimised away, so the actual backup size should be smaller once it's finished.



As others have said, you might want to consider a bigger drive, as one the same size as your internal drive means you'll have limited backup history, but that doesn't mean you can't use one the same size. There's a lot of stuff that Time Machine backups up by default, but which you don't necessarily need, so with that in mind you can make it work if you want.

I'd start by going into the Time Machine preferences and under options, select your System folder (inside your startup volume), you'll be asked if you'd like to exclude all system files and applications, say yes to this, as you can easily reinstall these from your recovery partition (which Time Machine *also* backs up, so it's just wasting space to back these up twice).

Next you'll want to look for good candidates for excluding; I tend to exclude all applications that I know I can just download again, like Adobe Creative Cloud apps, apps from the app store and so-on.

Other things to exclude will be up to you; if you use syncing services like Dropbox you'll probably want to exclude that folder. I also excluded my Downloads folder because nothing I download should stay there for long.

I also excluded my /Library/Application Support folder, as this tends to just contain stuff that will be reinstalled by the apps that require it (any actual data should be in your user folder).

If you're still having trouble, you can just exclude some folder(s) temporarily; exclude enough to run the initial backup, then once that's done, remove the exclusion and run a new backup to finish backing up your system. This works because the padding is calculated primarily based on the size of the backup, plus the first backup likely won't have used as much space as Time Machine originally calculated.
 
Last edited:

BLBL

macrumors 6502a
Apr 11, 2018
844
125
Many thanks for your very informative post. I guess I can make this work by using just 120GB partition from external SSD for my 128GB MBP.

Now that you mentioned that TM also backs up recovery partitions and system files, does it still work so that you can drop this TM image to another different model MacBook (or iMac) just like that? In a same manner as you could use iTunes backup to any iPhone? It is clever enough to exclude unnecessary things when restoring to different machine so that it is not messing up destination machine?

I already made my first backup test by doing full TM backup and it wrote about 20GB data on external ssd, it said estimated space needed for backup a little over 30GB, so it was plenty overstated. So I guess even with more data it should be still OK as it will write this over older backups.
 

haravikk

macrumors 65816
May 1, 2005
1,494
19
Now that you mentioned that TM also backs up recovery partitions and system files, does it still work so that you can drop this TM image to another different model MacBook (or iMac) just like that? In a same manner as you could use iTunes backup to any iPhone? It is clever enough to exclude unnecessary things when restoring to different machine so that it is not messing up destination machine?
Recovery from a Time Machine backup occurs using Migration Assistant after the main system files have been installed/re-installed, though you can also run Migration Assistant at any time you like (you could run it right now if you wish, just to look at the options it gives you).

Migration Assistant makes it easy to fully restore applications, user accounts and system settings, and it shouldn't overwrite anything unless you tell it to. However it may not be suitable in some cases, for example if you already have the user accounts you want, and just want to copy some files.

In that case you can simply browse a Time Machine disk (from any Mac system) just like you would any other folder structure in the Finder; this lets you locate and copy files and folders just like you would from any other source, though you may need a password to unlock the disk (if it was encrypted) and may need to enter an admin password to copy the data.

I already made my first backup test by doing full TM backup and it wrote about 20GB data on external ssd, it said estimated space needed for backup a little over 30GB, so it was plenty overstated. So I guess even with more data it should be still OK as it will write this over older backups.
Yeah the padding that Time Machine allows can be a bit ridiculous; it's primarily calculated based on how much you're backing up at the time though, so you can trick it a bit when it becomes a problem.

So if you're backing up to a 120gb drive, and need to backup 100gb of data you might find Time Machine's padding prevents it from running, but if you just exclude some stuff so that the first backup is only 80gb then it will run quite happily. Then when you remove those exclusions, you'll only be backing up 20gb of "new" data, with 40gb free.


Time Machine is definitely good for a bundled backup solution, and of course it's very well supported within macOS, but it does have its quirks and annoyances!
 

BLBL

macrumors 6502a
Apr 11, 2018
844
125
Sounds about what I have been looking. So basically if I would get a new machine or I reformat my current one and begin OS installation process to moment where is ask if you want to set it up as a new machine or restore from TimeMachine, I can select the latter and come up with the system I had at the time when that backup was made on external drive? How it handles accounts, like if I had iCloud, iMessage or Facetime in use? Are they set up automatically on new machine from backup?
 

mpainesyd

macrumors 6502a
Nov 29, 2008
639
154
Sydney, Australia
Yes to all your questions. You will need to enter some account passwords but then the new installation should work exactly the same as the previous one when the last TM backup was made. I just went through this with a replacement iMac.
Migration Assistant can also copy the files and setup directly from another Mac on the same network instead of a TM backup. This is a useful contingency if the Installation from TM fails (happened to me once several years ago - after that I started using at least 2 TM backup disks!). So it is worth keeping the old Mac around until the new installation working from the TM backup.
BTW - Migration Assistant is part of the setup process when you first boot a new Mac. You can ignore it and do the migration later but it is best to do the migration from the start if you have a TM backup available.
 

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