iCloud isn't a back up its just a sync service so you shouldn't rely on that as a back up.
Got a tip for us?
Let us know
Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
4TB Enough for Time Machine?
- Thread starter Biro
- Start date
- Sort by reaction score
I think the point JamesMay82 was trying to make is that he has multiple copies of his data.
That's definitely not my experience at all. There was a time, I believe during the El Capitan days, when Time Machine would occasionally and randomly decide the backups were invalid and would wipe them all out and start over again. That was very not good, but Apple did fix that in the next OS, and it's been solid since then. Granted I skipped over 10.15, 11, and 12, so I can't speak for those. Also Time Machine uses APFS now, which is more robust.
Also how much you exclude from Time Machine backups. I tend to have a fair amount of temporary data that changes a lot and is trivially recreated if needed, so there's no point wasting hundreds of gigs of backup space on that.
True, although I don’t worry too much about excluding things apart from my Parallels VM which is backed up elsewhere.
In a real life scenario, most data hardly ever change and therefore is backed up only once on TM. Also, for what I do I don’t need to have a daily history of back ups to fall back to. I only need the one. Any more than that is just a bonus. Keep in mind I also keep CCC backups which I refresh about monthly.
HobeSoundDarryl
macrumors G5
4TB will work with a total of 2TB to backup. My general recommendation is total storage to backup TIMES (at least) 3, or 6TB in this case if not more. And since you are including an external to backup, I'd probably imagine forward in time to see what size external I'm using in 3+ years too. Will that still be the 1TB drive or will you have perhaps added something bigger? You can buy a 5TB external HDD for < $100 these days and 4TB SSDs are below $200.
If you might fatten up that 2TB total, I'd best guess my future storage and multiple THAT times at least 3. If I best guessed that my future external might add something like that: 1TB internal plus 5TB external = 6TB times 3 = 18TB Time Machine drive.
Rationalization: there are TWO key concepts/benefits of Time Machine:
For the sake of illustration (and admittedly heavily oversimplifying in this example), let's imagine that 4TB in your case will give you backups of your files to maybe 40 days ago. If up to 40 days from now, you notice a lost or damaged file, you should have an easy ability to recover it. Up to 60 days from now, you should have an easy ability to recover a version up to 20 days old today. Up to 79 days from now you should have the easy ability to recover a version as far back as maybe yesterday's "save" of that file.
Again, this is oversimplifying for a kind of understanding of how TM works: it's really about file versions and not all files are getting backed up every day, so any given file might have an oldest backup actually MONTHS in the past in the above scenario.
However, the "catch" in not being able to travel back very far in time is the corrupt file or lost section/data file that you don't notice is corrupt or partially lost through many saves. Simple example: you are writing the great American novel and you accidentally deleted chapters 2-7 many saves ago, while continuing to write latter chapters. You may not notice this at all as you continue to write... but the updated copies of the book file are being written into your TM space with those missing chapters still missing.
One day you reach "The End" and you decide to give it a good proof read from the first word, Chapter 1. Here's where you realize that somewhere along the way, you accidentally deleted Chapters 2-7. Panic. Peril. Disaster. Angst. But wait, "I can recover them from Time Machine backups." So you start TM and begin stepping back in time in search of those lost chapters. If you have enough storage, you will be able to find a version that still includes those Chapters and recover them. Copy & paste them into the final document and the book is whole and complete. Hooray! Pulitzer prize incoming.
However, if TM storage is pinched, you might find that the oldest possible copy is one that also lacks those chapters... that the version of that file that included those chapters became oldest backup some time ago and was overwritten to create space for newer versions of the book file. If so, you get to attempt to recall and rewrite those chapters from scratch again. There's always next year+ to try for that Pulitzer.
Bottom line: too much TM storage is superior to playing the "what's the minimum?" game. If you only care about recent backups, you could probably go < 4TB. But if you want the core feature of TM, buying more space means buying more time travel capability. Instead of being able to only step back- say- 20 days (actually file versions) in the earlier example, abundant space might give you a 100 days (versions) or 200 days (versions), significantly increasing the odds of recovering about ANYTHING you discover is lost/mistakenly altered/corrupted (and many saved versions newer than the first corrupted file are corrupted too)/etc.
I hope this is helpful.
One more thing: while it's great that you are proactively thinking about backups (many don't until a dead or lost drive makes recovery urgent), consider that a much better idea is to get at least one recent TM backup OFFSITE. The simple way to do this is to purchase TWO drives for TM, set both up as TM drives and regularly rotate the two from OFFSITE to ONSITE TM backup. This protects data against fire/flood/theft scenarios. It does little good to have both your master copy (on Mac) and your TM copy at the same location in those scenarios: you will lose all.
However, if one recently updated TM backup is OFFSITE, the odds of near full recovery goes up dramatically. I store my OFFSITE TM backup in a low-cost bank safe deposit box and rotate them every 30 days. Worst case for me is fire/flood/theft on day 29. Then I might lose the most recent 29 days of new files.
Someone else might argue for some kind of cloud service for this OFFSITE option- and that has some merit. My own personal preference is to control my data myself vs. trusting complete strangers "in the cloud." So I rotate drives as described. But cloud can help here and, admittedly, very recent files I work on will sometimes be in Dropbox or iCloud to easily work between several Macs I own (effectively being a fresh "third" backup of most recent files).
The best backup approach is going to utilize this kind of strategy. At least ONE recent copy stored safely somewhere else is huge in terms of data peace of mind. You are already thinking in the right direction with at least ONE backup. Add one more like this and regularly rotate the drives and you'll have much greater security for ANY scenario.
If you might fatten up that 2TB total, I'd best guess my future storage and multiple THAT times at least 3. If I best guessed that my future external might add something like that: 1TB internal plus 5TB external = 6TB times 3 = 18TB Time Machine drive.
Rationalization: there are TWO key concepts/benefits of Time Machine:
- Backup your files. As is, 2TB would be fully enough for 2TB of storage.
- Go "back in time" to recover an old version of some file(s) now lost, corrupted, etc. The smaller your TM storage the less time available to do this. In other words, less storage reduces how far back in time you can go.
For the sake of illustration (and admittedly heavily oversimplifying in this example), let's imagine that 4TB in your case will give you backups of your files to maybe 40 days ago. If up to 40 days from now, you notice a lost or damaged file, you should have an easy ability to recover it. Up to 60 days from now, you should have an easy ability to recover a version up to 20 days old today. Up to 79 days from now you should have the easy ability to recover a version as far back as maybe yesterday's "save" of that file.
Again, this is oversimplifying for a kind of understanding of how TM works: it's really about file versions and not all files are getting backed up every day, so any given file might have an oldest backup actually MONTHS in the past in the above scenario.
However, the "catch" in not being able to travel back very far in time is the corrupt file or lost section/data file that you don't notice is corrupt or partially lost through many saves. Simple example: you are writing the great American novel and you accidentally deleted chapters 2-7 many saves ago, while continuing to write latter chapters. You may not notice this at all as you continue to write... but the updated copies of the book file are being written into your TM space with those missing chapters still missing.
One day you reach "The End" and you decide to give it a good proof read from the first word, Chapter 1. Here's where you realize that somewhere along the way, you accidentally deleted Chapters 2-7. Panic. Peril. Disaster. Angst. But wait, "I can recover them from Time Machine backups." So you start TM and begin stepping back in time in search of those lost chapters. If you have enough storage, you will be able to find a version that still includes those Chapters and recover them. Copy & paste them into the final document and the book is whole and complete. Hooray! Pulitzer prize incoming.
However, if TM storage is pinched, you might find that the oldest possible copy is one that also lacks those chapters... that the version of that file that included those chapters became oldest backup some time ago and was overwritten to create space for newer versions of the book file. If so, you get to attempt to recall and rewrite those chapters from scratch again. There's always next year+ to try for that Pulitzer.
Bottom line: too much TM storage is superior to playing the "what's the minimum?" game. If you only care about recent backups, you could probably go < 4TB. But if you want the core feature of TM, buying more space means buying more time travel capability. Instead of being able to only step back- say- 20 days (actually file versions) in the earlier example, abundant space might give you a 100 days (versions) or 200 days (versions), significantly increasing the odds of recovering about ANYTHING you discover is lost/mistakenly altered/corrupted (and many saved versions newer than the first corrupted file are corrupted too)/etc.
I hope this is helpful.
One more thing: while it's great that you are proactively thinking about backups (many don't until a dead or lost drive makes recovery urgent), consider that a much better idea is to get at least one recent TM backup OFFSITE. The simple way to do this is to purchase TWO drives for TM, set both up as TM drives and regularly rotate the two from OFFSITE to ONSITE TM backup. This protects data against fire/flood/theft scenarios. It does little good to have both your master copy (on Mac) and your TM copy at the same location in those scenarios: you will lose all.
However, if one recently updated TM backup is OFFSITE, the odds of near full recovery goes up dramatically. I store my OFFSITE TM backup in a low-cost bank safe deposit box and rotate them every 30 days. Worst case for me is fire/flood/theft on day 29. Then I might lose the most recent 29 days of new files.
Someone else might argue for some kind of cloud service for this OFFSITE option- and that has some merit. My own personal preference is to control my data myself vs. trusting complete strangers "in the cloud." So I rotate drives as described. But cloud can help here and, admittedly, very recent files I work on will sometimes be in Dropbox or iCloud to easily work between several Macs I own (effectively being a fresh "third" backup of most recent files).
The best backup approach is going to utilize this kind of strategy. At least ONE recent copy stored safely somewhere else is huge in terms of data peace of mind. You are already thinking in the right direction with at least ONE backup. Add one more like this and regularly rotate the drives and you'll have much greater security for ANY scenario.
Last edited:
My old LaCie is a 2TB HDD. The only things I am thinking of moving to the external Samsung T9 drive are my photos, which I can also back up to the cloud. Right now, I’d be using Amazon’s cloud, which I get as a part of Prime.
I’m not sure I want to pay for extra iCloud capacity from Apple. Besides, iCloud is more of a synching service. You CAN use it as a backup - for small things - but I don’t think that’s the primary purpose.
Also, I’m pretty sure I won’t be looking to restore from versions all that long ago. More like just before whatever failure or mistake resulted in a loss of data.
I appreciate the feedback. It’s an interesting discussion.
Last edited:
A better bet for photo backup is not using TM for that drive. Just use SuperDuper or Carbon Copy Cloner to clone the photo drive and ideally store the copy offsite (or at least in a fireproof safe, in case the worst happens). TM is a good backup solution for your main system drive and the one on which you do most of your work with smaller files, like the text files you mentioned. Because of their small size, you'll end up with LOTS of history on these kinds of files.
Come to think of it, if you're working with RAW files for your photos TM might be a good solution for them, after all. I know Adobe creates xmp sidecar files for your photos and doesn't touch the original RAW file from your camera when you make edits, so in theory all you'd need to do to roll back to earlier versions would be to find an older version of the xmp file. You only need to consider switching backup methods once you've processed the photos into JPEG or whatever final format you use.
Come to think of it, if you're working with RAW files for your photos TM might be a good solution for them, after all. I know Adobe creates xmp sidecar files for your photos and doesn't touch the original RAW file from your camera when you make edits, so in theory all you'd need to do to roll back to earlier versions would be to find an older version of the xmp file. You only need to consider switching backup methods once you've processed the photos into JPEG or whatever final format you use.
That is exactly why I stopped using Time machine. It’s nice to know that has been fixed.
A slight bit of tangent, here (with no detriment to your Thesis)...
Though the Premise of iCloud is a Sync-Service, using your extra Space (via iCloud Drive) enables one to store what one may-well-decide.
I Sub to the 2TB iC+, and--after all the sync, backups, et al.)--I still have over 1TB of cloud Space to which I can upload anything I desire.
Smallish, on the grand scheme of cloud-things; but, nevertheless, I can create folders, store any form of data, and access it (personally (privately?)) any time I desire.
I use most of that Space to store photos/videos of my cats, of course
It also depends on how long you want the backups to be available and how often the data changes. The 2x rule of thumb is a quite reasonable one.
As one example, I'm a pro photographer. I have about 11 TB of live data on 18TB of storage, most of which is never modified (original captures). I have 16TB Time Machine drives, and at this point I have a couple of days less than two years worth of backups on each TM drive - and there is about 2TB free on each.
The person that said that 6TB is a minimum for the OP's specification is wildly off base.
PS I *also* store archive copies in a cloud (AWS Deep Glacier) but that's the fourth, off-site copy and is not updated in real time.
As one example, I'm a pro photographer. I have about 11 TB of live data on 18TB of storage, most of which is never modified (original captures). I have 16TB Time Machine drives, and at this point I have a couple of days less than two years worth of backups on each TM drive - and there is about 2TB free on each.
The person that said that 6TB is a minimum for the OP's specification is wildly off base.
PS I *also* store archive copies in a cloud (AWS Deep Glacier) but that's the fourth, off-site copy and is not updated in real time.
How do you “upload” data to iCloud independently from synching?
If you keep the Optimisation option switched off (as I do) as far as I know you are any limited to the space of your system disk.
I’d love it if you could show me a way to upload something independently from the synching of data.
Last edited:
HobeSoundDarryl
macrumors G5
I’m “the person” and did NOT write that it is minimum but my general recommendation (a times 3 approach instead of times 2). The cost difference of 6TB HDD vs.a 4TB HDD might be $20 with some shopping around (just checked and it’s only $13 on Amazon). And OP probably can’t know that their 2TB current core storage doesn’t become 3TB (or more) in the next few years. If it did, then the “times 2” approach would still fit the 6TB TM storage they would already have.
I don’t grasp any push back about buying more than bare minimum… with 20TB HDDs available well below $300. Any person could add $20 to $50 to any minimums thinking to probably double or triple their TM space. Drives last a LONG time. Some “future proofing” beyond minimums is dirt cheap for this kind of purchase.
Yes, that could be overkill in the immediate present… but does base storage fatten up over the next 3-5 years? Does OP add a second Mac? Or move someone in that needs backup space too? With big storage priced so cheap, one can easily, proactively cover about any unknown future need instead of buying bare minimum for right now and then having to buy a new minimum when core storage evolves next year or two….or three… as it often does for many computer users.
If OP is thoroughly dollar pinched, “the person” also offered that 2TB of storage could back up 2TB of Core Storage. Buy 2TB HDD for minimum cost (maybe $40-$50 less than 6TB) and use CCC or SuperDuper instead of wasting spare space with TM version copies.
If OP isn’t going to fill 50% of their 2TB core space, save $6-10 more dollars with a 1TB drive and use Chronosync to backup only their own files.
However, I’m doubting $6 to $50 is a lot of money for ANY Apple tech owner. So I encourage some “think different” here… especially since one could go nuts for 20TB for about AirPods Pro pricing. 5 Apple handkerchiefs can buy 5-6TB. One ASD stand option could cover 16-20TB.
Post #1 says OP owns an M2 Max Mac Studio and paid up for 1TB Apple SSD storage. I'm doubting OP is so pinched that they need price minimization here. The presumably $200 they paid for 512GB of more Apple SSD storage in that Mac could easily buy them 16TBs or more of TM storage. If they wanted to heed my "one more thing" suggestion, it could buy them TWIN 10TB (or more) drives so one could also be recently backed up and always stored offsite.
Last edited:
I would say that you want the disk drive that is twice as large as the data you want to back up. So if you Mac has a total of 2TB storage, in the worst case it could have 2TB of data. Then buy a 4TB disk. But large disk will allow you to keep more older versions of your files.
That said, what kind of data do you have? If it is a collection of downloaded movies, then the data will never change. You are not editing those movies so there will be no older versions to keep and even 4TB is overkill.
But if the data is "live" and you are making changes to most of it frequently then you might want to keep older historic versions of the files. 8 or even 10 TB disks don't cost much more then 4TB disks.
Finally, consider some kind of redundant backup, in addition to the TM disk. The threat is (1) theft of equipment which will take the TM disk and the computer, (2) house fire, (3) lightning hitting the power pole outside and taking out the computer and the TM disk. Keep a second copy off site or at least in a fire safe. Cloud backup works well as does a second or third TM drive.
The above is correct. 3 is better than 2.
But,... is the data live? If the data is just downloaded movies then the data is not likely to change, ever. You are not making changes to the files. In this case 2X is good enough. But if the data is live and is constantly being edited and changed then you need a lot more room to hold all the change history.
Finally the 2X or 3X number applies the data that gets backed up, not the storage size. TM does not backupsystem files that can be re-downloaded. and your storage might not be full
But I agree, if you van get a much larger drive for only a little more, go for it. But if budget is an issue, better to spend money on a second redundent system then to overspend on only one system.
Make sure that the Settings > iCloud > iCloud Drive > "Sync this Mac" is enabled.
In Finder > Settings:
Enable iCloud Drive:
I may be playing loose with the term 'sync', but AAPL is really not very granular in expressing the meaning of "sync" as it could be, which is probably why there is some confusion over the matter.
With iCloud Drive enabled, apps and devices can access Content in iCloud.
Some of this can be seen, and some cannot.
In Mac OS when I choose to keep my 'Desktop & Documents Folders in sync with iCloud', contents therein are automatically mirrored to the storage in my Systems.
Folders and documents I have created/stored in iCloud outside of those two Spaces are reflectively available.
Locally when I enable iCloud Drive in Finder, as above . . . or via icloud dot com, iCloud for win64, etc. (this is where the water gets a little muddy for me, as I don't spend a great deal of time accessing such outside of Mac OS).
I can still access, edit, delete, etc. all my (how shall I better say it?) "reflected-but-not-mirrored" content, but it is my choice whether to download them Locally.
In this sense, to me, it's basically just another Network Share.
hth
OK, I see where you are going with this but I am still confused.
Yes I can create a folder on the iCloud Drive, independent from the mirrored Desktop and Documents folders, but to do so I still have to copy the data to my local system disk as there is where the iCloud Drive resides.
Let's say that I do have the space to do so, I would assume that the moment I want to clear up my local space, the online iCloud folder will simply synchronise with my deletion, no?
EDIT: I guess I don't have to delete, I can just do the "remove download" option. Still it doesn't solve the problem that I need to first copy the data to the local disk for it to be uploaded in the first place. This would not be possible in my case if I wanted to upload my Movies files, which are held on a separate disk. I simply don't have enough space on the system disk to do so.
While we may have a different take on these matters (and certainly terminology, I appreciate your zealousness. It reminds me of my days of company backup tapes and rotation schedules.
If entire backups were being done by TM, I might lean towards your view on requiring such large volumes. However, TM best I recall is incremental and as such requires far less volume space unless each day notable amounts of data is added or altered. I might guess this is what others here too believe in real world requirements for TM dedicated volume space.
I think most would find 4 terabytes to be a great size for TM under normal scenarios of end user usage. Those with specialized needs may not care to depend on TM but rather store the data elsewhere. I use TM with my Studio Max M1 (for those that need to know - 64 gigs RAM and 1 terabyte drive). My TM drive is a 2 terabyte SSD. I also use NAS and cloud storage for my work files (mostly photo restoration, media library, and sensitive data).
Most home users don’t and wont go the distance you suggested. In fact most wont bother going as far as what I do. A simple TM on a single drive makes most happy and serves their purpose. I would advocate along with you that storing data should be done with a system that may engage typical basic disaster recovery (Multiple copies with multiple resting locations).
Thoughts?
as @MRxROBOT said the point was that I have different copies of my data. For example, I keep a copy of the photos I edited on the cloud and a copy of the originals in my external hard drive
Small volume users limit themselves in data depth and do not realize it. They also do not really understand the data storage policy (what number of backups will be available for months, years), have a vague understanding of how much space will be taken up by weekly backups and how much by monthly backups. They don't consider the risks of data loss and limit themselves in the flexibility of setting the frequency of recovery point creation via TM, intervals or other backup programs or simply ignore it. Someone said that 4TB is enough, so they will mindlessly copy everything. But they're wrong.....
Backups cannot be stored in the same place as the data being backed up. If you store a backup on the same disk array as your data, you will lose it if the primary disk array is damaged.
Mirroring (RAID) cannot be compared to a backup. RAID protects you only from a hardware problem with one of the disks (and sooner or later there will be such a problem, because the disk subsystem is almost always a bottleneck on the server). Besides, when using hardware raids there is a risk of controller failure, i.e. you need to keep a spare model.
Backups should be stored somewhere on a separate storage.
It's worth remembering that needs change....
Here is the formula for calculating the backup taking into account data growth per day (e.g. a person has suddenly developed a hobby of shooting video for hours or taking more and more photos), this will not take into account the compression size :
Future Used Data HDD/SSD= Used Size HDD/SSD x ( 4 + 10% ) ^ (Day N/365)
Last edited:
Once again you are assuming people don’t know what they are doing.
That’s a bad starting point for any discussion.
What you have decided to keep ignoring is that most small users change very little data over a long period of time.
You referring to the “data storage policy”, well, guess what, in their house people make their own policy.
Yes, I accept that an incredibly high number of people don’t think about backups at all, and they are the ones losing all of their data at the first hurdle, but to think that individuals backup needs are the same as enterprise is a ridiculous concept.
Individuals have a good grasp of how much data they change and when.
Individuals can and (most) do keep an eye on how quickly their TM disk is filling up, and if after 3 or even 6 months it is only half full then you are more than OK in terms of your ability to roll back a file to a safe point.
Some individuals, as all should, keep multiple copies of backups made in different ways and store them both on and off site. Some even store yearly snapshots on dedicated disks over and above all of the above.
Frankly, having a huge TM disk is not very useful if it is your only backup and it fails.
Some individuals have worked in enterprise settings and they appreciate that a person/family is not an enterprise.
A formula that works well for Procter & Gamble does not necessarily work equally well for grandma or Jonny the gamer or even Bob the musician, etc…
I think you distinguished the difference between your plan or statement when you said “small volume users“ (as opposed to SOHO and larger scale companies). Home users don’t need all that you mention unless as stated, they are doing something specialized that generates new files whether added or past files edited.
Your formula is reasonable as a possible starting point. However one could start smaller and see the rate of growth of the backup volume (full plus incrementals) and elect later to increase the volume whether by replacement or addition depending on the nature of the files and potential need to access.
cheers
I'd guess 4 TB is fine, but no one here seems to have mentioned the obvious—since you've been using TM for a while, this is something you're best postioned to determine youtself.
Will your usage on the Studio be significantly different from that on the iMac? If not, you can just look at your old TM backup to determine the rate at which your backup size increased. From that, you can extrapolate how long you can keep backing up to a 4 TB drive until TM needs to start pruning.
Specifically, according to Apple Support, "Time Machine automatically makes hourly backups for the past 24 hours, daily backups for the past month, and weekly backups for all previous months. The oldest backups are deleted when your backup disk is full."
Thus you want to go to Disk Utility and see how much is stored on your old TM drive, in GB. Call that "S". Then go into Finder and see how far back that goes in weeks. Call that "T". Then scan through your weekly backups and get an estimate of how large they are, on average, in GB. Call that "W"
Then the number of weeks you'd last before TM would need to start pruning a 4 TB drive should be around:
T + (4000–S)/W.
For instance, if S were 1500 GB, T were 60 weeks, and W were 10 GB, that tells you in the first 60 weeks you'd use up 1500 GB. That would leave you with 2500 GB, which you'd use up at a rate of 10 GB/week, so it would last an additional 250 weeks, for a total of 60 + 250 = 310 weeks. Now let's confirm the formula works:
60 weeks + (4000 GB –1500 GB)/(10 GB/week) = 310 weeks = 6 years.
Also, TM really isn't a backup system, it's a versioning system that allows you to access older files that you've changed or deleted. It works brilliantly for that, but that feature adds a lot of complexity that in turn reduces its robustness. I use a TM backup on my 2019 i9 iMac running Monterey, and once every six months or so it stops working and has to be wiped and restarted.
You've probably had better luck, but I'd still recommend two additional backups, separate from the TM drive, created using something like Carbon Copy Cloner, which (unlike TM) is dedicated backup software. I've used CCC for maybe 15 years and, unlike TM, never had any corruption with it. One of the backups you'd run every night. For the other you'd run a backup and then store it in a remote location, like a friend's house or a safety deposit box, updating occasionally. That's the only way you're protected from theft and fire (or you can use the cloud instead of the latter).
Last edited: