Snapshots! To have, or not to have, that is the question?

[pine man]

I have been reviewing my Back Up strategy, which is, at the moment, hourly back ups to Time Machine and a daily back up via Carbon Copy Cloner to an APFS formatted SSD.

I have received some advice about Snapshots and CCC from Bombich and have also been reading other stuff about MacOS Snapshots and to tell the truth I am no wiser. As far as CCC goes I think I can see the merit in activating Snapshots in that software BUT what about the Mac Snapshots? Are they related to CCC Snapshots in any way and do I actually need them?

Any advice would be gratefully received.

 

[MacInWin]

Snapshots are backups taken when the backup drive is not attached and which are then incorporated into the next backup to the backup drive and then (supposedly) deleted. Because snapshots are stored on the internal drive, they are NOT for protection from drive failure, more for accidental deletions and maybe over-writes.

So, the assessment question should be, "How much risk do I want to assume? How much would I lose if I only backed up at x interval and had a failure one minute before x? Can I accept that risk?" Once you have that assessment of acceptable risk, the decision on a backup strategy for you should be simple.

If you cannot live without everything being backed up to within the last hour, you keep the TM drive attached and let it back up every hour. However, if you don't want to keep that drive attached, TM will do the snapshots until you do connect the drive. Just bear in mind that if the internal drive fails, you lose the snapshots, too.

In my circumstances, where I use my machine for nothing critical (surfing, some writing, email, etc) I don't don't need hourly backups at all, so I turn off TM and invoke it using a third party product called Time Machine Editor. I set it to backup twice a day. Because TM is off, there are no snapshots except that when TM is turned on by TME, then TM makes a snapshot then. So I have two snapshots, taken 12 hours apart. Never more, never less.

CCC I use once a day. I don't need it more than that. So I have snapshots turned off on CCC.

As for advice on snapshots, it's entirely up to you, but snapshots do take up drive space, particularly if you have high volatility large files you work with. In that case you might be better off making more frequent backups rather than relying on snapshots. Remember, you lose snapshots if the internal drive goes south.

 

[pine man]

Thanks for that very quick response.

At the moment I am happy to have TM do the hourly back ups and I will probably keep the daily CCC back ups with Snapshots.

I suppose that my ultimate aim is a rapid restore to operation in the event of the main drive going south and the above should cover that nicely. I am not so sure that the Mac Snapshots will be as much, if any use, and they mey get turned off. I think I am correct in saying that turning off Mac Snapshots will not affect the use of Snapshots with CCC.

 

[MacInWin]

I think that is correct, that TM snapshots and CCC snapshots are separate things. But it really doesn't matter, I think, if they are the same in your setup as CCC will make them if you set them up.

 

[IWT]

And to prove that Jake is not alone, I too follow his strategy.

I have an iMac, attached to which are two EHDs as Time Machine backups (modern OSs allow up to two TM Drives attached). I have "Backup Automatically" turned off and manually invoke a TM backup on a regular basis. Of course, this requires that I (or you) remember to do this.

But the great advantage is that only one snapshot is associated with each TM backup, the previous one from the last BU being deleted before TM does its job.

I also have CCC. I have snapshots turned off, but I think (only think) that CCC needs just one snapshot for proper working. If I'm right, like TM, it deletes the previous one before creating the new.

To answer your last point, pine man, TM snapshots and CCC snapshots are in no way associated with each other.

Ian

 

[pine man]

Thank you both.

Given that I am not at all short of space on my internal drive (about 85% available) I'll leave everything as it is, including Snapshots, so I have differing options depending on what chaos develops!! So far I have been a Mac user for over five years on the same iMac and the only thing I have ever used any of my back ups for is an occasional file that I shouldn't have deleted. Touching wood furiously as I made that bold statement.

 

[chscag]

Unless Bombich has changed the behavior of CCC snapshots, they are not removed as new ones are made. They simply build up using drive space. Which is why I have them turned off for CCC.

As for Time Machine, it no longer matters whether the backup drive is attached or not, a snapshot is made and stored as each backup is completed. However, Time Machine unlike CCC does remove older snapshots. As far as I know, Time Machine started doing this with the implementation of APFS and High Sierra.

Are snapshots something you need? I don't find them useful but that's something you need to decide.

 

[IWT]

I think you are correct, Charlie. I have CCC snapshots turned off. I wrongly thought that they created one, deleted it, new one etc. But I reckon you are right - none at all. Certainly, none show up.

And Time Machine. I do it manually. With two TM backups and CCC and with Photos & iTunes Libraries & Documents backed up separately, I'm pretty well covered

Ian

 

[ferrarr]

Unless Bombich has changed the behavior of CCC snapshots, they are not removed as new ones are made. They simply build up using drive space. Which is why I have them turned off for CCC.

As for Time Machine, it no longer matters whether the backup drive is attached or not, a snapshot is made and stored as each backup is completed. However, Time Machine unlike CCC does remove older snapshots. As far as I know, Time Machine started doing this with the implementation of APFS and High Sierra.

Are snapshots something you need? I don't find them useful but that's something you need to decide.

Aren't they removed when you make new clones if you have "Smart" enabled?

 

[chscag]

Aren't they removed when you make new clones if you have "Smart" enabled?

You mean the "Safety Net"? Not sure what you're referring to by "Smart" enabled?

What I do know is that regardless of how many new clones you make with CCC, unless you have the snapshot option turned off, those snapshots will accumulate and take up drive space. I have been over this before with Mike Bombich and he referred me to their knowledge base which says just that.

Again, I don't find the snapshots useful but someone else may feel that they are needed.

 

[ferrarr]

Yes, that was what I meant. I haven't used CCC in a while.

 

[pm-r]

To answer your last point, pine man, TM snapshots and CCC snapshots are in no way associated with each other.

Ian

And in case anyone else that's reading this thread was a bit confused as I was, and I was mistakingly thinking that the CCC snapshots was the same thing as the CCC SafetyNet, the differences are explained here:
Leveraging Snapshots on APFS Volumes | Carbon Copy Cloner | Bombich Software

Not quite the same thing but just in case someone else was confused...

Note: Snapshots are only available for APFS-formatted volumes on macOS High Sierra and later.

- Patrick
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[pine man]

And in case anyone else that's reading this thread was a bit confused

I was confused and now I'm only a bit confused! However my strategy, at the moment, will stay with all Snapshots activated and I'll review it next year after Catalina has been running for a while.

Thanks everyone for your input.

Edit: 15:27

pm-r

Just read your link to Levering Snapshots on APFS Volumes. Very helpful and I think I'm a little bit wiser now and happy that my strategy is good but needs a close look from time to time to make sure Im not over run with the little blighters!!