Disable local snapshots in High Sierra with APFS

My suggestion is you call Apple support ( 1-800-692-7753 ) and insist on speaking with a senior advisor because this is a bug in the High Sierra operating system which the senior advisor will report . Don't correct this on your own because this report will support an update to High Sierra and you can be one of the hero's to getting this much needed fix to the macOS .

An APFS snapshot is done with copy-on-write and tracking of allocated blocks. That means that very little is written to create one, just enough to account for multiple references to metadata and storage. Because there is very little writing involved, there should be very little wear (esp. compared to local snapshots before High Sierra!). And they should be very quick, almost instant.

A snapshot is not free, though; as the current filesystem diverges from the snapshot, it uses more space. In the extreme, it could use as much space as if it were a regular copy (i.e. once every block was different between the snapshot and the base filesystem).

The snapshots do mean that less free space is available than otherwise would be; but the Time Machine snapshots are supposed to be automatically deleted. If you sometimes run very full, that could be a problem; otherwise, they're useful and much cheaper in time, CPU, battery, wear, etc. than Time Machine snapshots prior to APFS and High Sierra.

I use Growl and HardwareGrowler; Growl can be given an AppleScript to do automatic actions based on certain notifications, and HardwareGrowler generates notifications of disk mount or eject, power changing from AC to battery, etc. My script would disable Time Machine and eject the backup disk when AC power was removed. It also disabled local snapshots, regardless, since I didn't want them. (It also enabled Time Machine when the external backup disk was again mounted.) Given that "tmutil disablelocal" no longer works, I should remove that from my script. Other than that, I don't guess I'll care too much.

Supposedly, OS updates (the minor ones that only need one reboot) may also create snapshots...not a bad idea IMO, since apparently one can always boot the Recovery partition and restore from one of those if needed. I wouldn't want to turn _that_ off, even if I could stop the regular Time Machine snapshots from happening.

There is a small problem. A lot of apps don't recognize the "purgable" files and therefore thinks that there is no avaible space on the drive for some operations. For people who might need some more drivespace to install stuff, snapshots might get in the way. For example, bootcamp instalations don't recgnize that here is purgable space, and can't make big partitions because of that, even if you free space. You have to wait hours, maybe days to have that space back actually instead of a single backup before the operation. It's a hassle sometimes.

fe_quirino wrote:

There is a small problem. A lot of apps don't recognize the "purgable" files and therefore thinks that there is no avaible space on the drive for some operations. For people who might need some more drivespace to install stuff, snapshots might get in the way. For example, bootcamp instalations don't recgnize that here is purgable space, and can't make big partitions because of that, even if you free space. You have to wait hours, maybe days to have that space back actually instead of a single backup before the operation. It's a hassle sometimes.

Apps dont make that decision. Apps make the request for unallocated space to the kernel. If the kernel doesn't unallocate that space, then you have an entirely different problem. Bypassing the kernel's i/o & disk management is absurd.

Argh...All this is ridiculous! I have to use ESET End Point Protection because of work and now EVERY TIME there is a 'local snapshot' it thinks that its a new drive, so every 10 minutes its asking me if I want to scan it....driving me crazy. WE NEED TO BE ABLE TO DISABLE THIS. I have my own Time Machine drive that I use, I don't want this ridiculous secondary snap shot. HELP APPLE!!

Thanks, but I'm not sure you're addressing my issue. It may be that my computer was always doing this silly local snap shot, but from what I can tell, this is new because I now have a list of local snapshots only beginning the day that I downloaded High Sierra. I also have my own backup drive for time machine already in place. There is no reason to have the local snapshots with my TM there...its an unnecessary redundancy. The real nuisance is that my antivirus software thinks that every time there is a local snapshot taken, that its a new drive, and so asks me if I want to scan this new drive. Always. This was never a problem before I upgraded to high sierra. this is a new thing and its annoying. There must have been some configurational change to affect this... but how do I stop it from happening. I'm not allowed to remove my Antivirus as its institutionally mandated. The only other thing I can think of is stopping the local snapshot. If I have time machine backing up every hour to my external drive then I don't need local snapshot doing the same thing. Unless it was already doing this, but it was invisible before and so my AV software wasn't detecting it.

Strange.

There is no reason to have the local snapshots with my TM there...its an unnecessary redundancy.

Local Snapshots are necessary for Time Machine to work.

I'm not allowed to remove my Antivirus as its institutionally mandated.

Either find another institution or have a Mac that isn't backed up, will never work properly, while increasing its exposure to malware and related threats. Your choice.

A third option is to fire the incompetent idiots mandating your antivirus software. That's my favorite because it saves institutions tons of money. I take only a small percentage.

C'mon Apple, this is just taking your loyal customer base for fools.

I've just had to turn down a short-notice paid remix job because I couldn't get space on my hard drive for reinstalling a couple of apps and their associated samples. After reading this I thinned the snapshots on my laptop SSD (256GB) and free space suddenly went from 15GB free to 130GB free. The snapshots had already been backed up, so I can't see why Time Machine needs to maintain them.

Yeahyeahyeah I know, buy a larger hard disk, but A) the space is there, just being hogged by these snapshots and B) Don't try to tell me the fix to something you created is to spend more money on your products - that's a justification that a heroin dealer would use, not befitting the manufacture of elegant technical products.

Where in the Developer Forum post you quoted is

sudo tmutil disablelocal

mentioned? The entire context is different -- it's how to allow local snapshots separately from the normal TM backup, not how to allow normal incremental TM to the specific user-defined backup volumes while at the same time disabling all local backup.
In fact, the Developer Forum thread you reference says (Sept./November '17) that "sudo tmutil disablelocal" causes TM to be disabled completely, see repsonses by "peter_voisin" and "M Tesla" .

If you have different sources for what you claim, please cite them,but otherwise, please be more careful.

I decided to sort of do away with local snapshots. I have a cron job that runs every night at 1AM and deletes them all.

0 1 * * * /usr/bin/sudo /usr/bin/tmutil thinLocalSnapshots / 10000000000 4

(I have my sudo running with NOPASSWD for my ID)

This has nothing to do with the life of the drive (which happens to be a SSD in my case) or general performance. The OS is writing hundreds of GB of invisible data to the storage device without giving power users the choice of managing how or if this process works. For people editing large videos, this can make the difference between completing the project or not, as After Effects and similar programs need empty disc space for caching.

I don't understand how someone can reap tens of thousands of points by posting "that's the way it is" comments such as this. Not helpful at all. And, it is not solved, so there should not be a green check mark next to your name. If you have a close connection to Apple in some way, then you should relay this problem to their engineers.

Apologies - this was meant to be a reply to someone else in this thread, who said snapshots will automatically get deleted as necessary)

Hi, this is not my experience. I think there is a bug (I am updated to on 10.13.3). I have a 1TB drive. My free space got down to 48GB. I needed to install a 60GB audio application and knew my drive shouldn't be that full
Deleting Local Snapshots freed up over 150GB of space.

This topic from the Apple Developer's forum might shed some light on this: APFS snapshots: where are they located? | Apple Developer Forums. See the reply by tclementdev.

I use photoshop which uses the local disk for scratch space. When it doesn't have enough disk space, it runs very slowly. That's very compelling reason to not want local snapshots.

Totally agree with this!

We should be able to decide whether we want local backups or not. The lifespan of the SSD will be indirectly affected by this change.