Optimize Mac Storage is all about making iCloud Drive work for Macs with limited storage, which for most people is going to be the case … It’s a rare few, who stump up the dollars for upgraded storage on their Macs, and so if they go ahead and push gigabytes after gigabytes into iCloud Drive, they’re going to run out of space pretty quickly.

So, the Optimize Mac Storage setting is intended to “offload” files so that they continue to live in iCloud Drive – in the cloud – but they are removed from your local copy, on your Mac … a “file name” is still shown but has a little cloud indicator next to it, indicating that it is no longer immediately available locally but you can download it from iCloud Drive when you want to work on it, view it, etc, etc. And the intended way it operates is that you right mouse click / bring up the context menu, select Download Now, to do so.

Now I have three Macs – 2 laptops, and 1 Desktop. Only the Desktop has enough space on its boot drive – the location for your iCloud Drive folder – to accommodate all of the files I’ve moved to iCloud Drive, along with the Operating System etc. As I mentioned above, all of these Macs, started with the Optimize Mac Storage setting On. I’ve since changed the setting on the Desktop to Off, because I DO want all of my iCloud Drive files stored locally on my Desktop. And I use an application called Sync Folders Pro, which I’ve used for years to keep the various cloud repositories in sync – between Google Drive, OneDrive and iCloud Drive.
However, I began noticing some odd behaviour. I only ever do this syncing on the Desktop, where I know – or thought I knew – that because there is ample space on my boot drive – all of the iCloud Drive files should be locally present. This is how I’ve got the local files for my 3 cloud providers organised:
- Onedrive – on external Fast Thunderbolt 3 RAID Drive
- Google Drive – on external Fast Thunderbolt 3 RAID Drive
- iCloud Drive – on internal SSD Boot Drive
You can imagine my surprise when after running one of my weekly syncs, I found that quite a large number of files appeared to be missing from my local iCloud Drive repository? Where could they be? It was at this point, I did do some reading, and this was where I became more familiar with the Optimize Mac Storage setting. So I realised that it made some sense for this setting to remain On for both of my laptops – so that their more limited storage didn’t try to keep the entirety of my iCloud Drive repository on their relatively small boot drives.
BUT, for my desktop with its ample boot drive size, I was going to turn if off, and hopefully that would make the files that were missing re-appear, be brought back into the folders where they were missing. By the way, I should point out that I’d logged onto iCloud.com, browsed to the online portal for iCloud Drive, and verified that the files that were missing in my local repository were all there in the online portal. So why weren’t they present locally? I had plenty of spare space on the boot drive of my Desktop, so I was a bit surprised they were “no longer there”.
I even left the machine on over night hoping that iCloud would rectify the situation and download the missing files. Unfortunately not. It didn’t happen.
The first thing I tried was, clicking on one of the folders that had “missing files”, and chose the Remove Download command. This is only present for iCloud Drive folders – and as the name suggests allows you to control whether a folder should be present locally or not. After that, both the folder, and all the files within it, acquired the little cloud symbol – but still the missing file wasn’t there. I then selected the command to do the opposite, Download Now, in the hope that this time, the complete directory would be downloaded – including the “missing file“. Nope, no dice.
I then went back to my file synchronisation software – Sync Folders Pro – which is really neat – and did another preview – effectively it showed me the actions it would take – if it were to do a synchronisation now. And while monitoring the directory in iCloud Drive where the missing file should be, I let it perform just that one synchronisation operation – not the whole lot – just that one.
What happened amazed me – that one file was copied into the directory – and then it promptly disappeared – it was deleted again! By iCloud Drive. The other key thing I realised as this happened, was that the missing file, isn’t missing because it’s not been downloaded – i.e. it’s not there, and has a cloud symbol, indicating it needs to be downloaded – it’s not there, because iCloud Drive “thinks” it shouldn’t be there. And that’s why iCloud Drive deleted the file when it was “re-introduced” to the directory.
So my only conclusion is that something in the manifest of files was now out of kilter / out of sync (get the pun) between the iCloud Drive’s “cloud based” repository, and my local iCloud Drive directory structure. How to fix this?
The steps that finally fixed it, and I really was “clutching at straws” here, but perhaps my experience might help others experiencing these symptoms, were these:
- I returned to the iCloud Drive online portal and deleted the online version of the MISSING FILE. Yes, it was with great trepidation I did this, but I figured this was the only way to bring the two versions “into sync”.
- On my Mac, I copied back the missing file into the local iCloud Drive directory, and waited with bated breath. Momentarily the cloud icon appeared – I believe that happens at the time when the file is being uploaded to iCloud Drive as well.
- I returned to the iCloud Drive online portal, and the “missing file was there”, reinstated.
- And to my absolute relief, it stayed in place locally.
My conclusions from this experience are:
- If you are planning on using iCloud Drive to store a significant volume of files, make sure you understand the meaning of the Optimize Mac Storage setting, and how it affects your particular Mac. For the vast majority of people, you will want to leave it set on, unless you’re one of the lucky few who have a Mac with a massive SSD, and large iCloud Drive subscription.
- Should you experience some bizarre behaviour with files that you do expect to be locally present on your Mac, or which appear to have “gone missing”, consider the steps I’ve described above. It appears likely they will still be available through the online portal version of the iCloud Drive, but it isn’t a particularly straightforward approach to get everything in “sync” again.
Hoping you found this interesting, and of course if you’ve got any further light to shed on the subject, I’d be very interested to hear it.