CleanMyMac???

[Dave2002]

Thanks for the advice and warnings. I suppose I could have checked this in the past, but never really did. I have enough kit now to be able to test out a few things, though your comments are alerting me to the idea that initially at least I should only delete things I will either be delighted to be rid of or perhaps merely not sorry to lose. Then I'll do some tests to work out as well as I can what the actions will be. There's also RTFM - though sometimes testing is more reliable.

Some email is in any case shared with other people, so if I really wanted to recover an email or attached document I should be able to - though the reality is that I'd probably be glad not to.

[Dave2002]

I have been wondering what exactly Apple meant by "purgeable" in relation to files, which is shown sometimes when doing a cmd-I request for file information, for some time now.

In macOS Sierra, “Purgeable” content appears when you've turned on Optimize Mac Storage. It's storage space that your Mac can automatically make available when storage space is needed. Files marked as purgeable can always be downloaded again on demand.

from this site - https://support.apple.com/en-gb/HT202867

This could be useful, though could it also introduce other problems? If files are deleted locally, and then have to be downloaded again later, that could really slow things up - but later on. I suppose that if one's system is short of resources that it's better to reclaim space "now" and get the immediate benefit, against a possible slower operation for some actions in the future.

Does this storage optimisation remove all of the purgeable files, or only what macos decides is in some way "optimum" for now?

[Dave2002]

Looking into this further I found this page - https://support.apple.com/en-us/HT206996

From which I found the following extract

Some categories allow you delete files directly. Move your pointer over the file name, then click the x button to immediately and permanently delete the file. If you purchased the file from the Mac App Store, iBooks Store, or iTunes Store, you might be able to download it again.

Note the use of the word "might" - so no guarantees that if you delete cluttter or allow Apple to decide that files are clutter that you'll ever get them back.

Presumably there's no indication of what files have been removed, so it's up to the user to notice that things are missing and download them again, or make a note of the deletions at the time. This is really rather poor.

I may have missed something though - there is the option to optimize storage, so how benign this is I can't say. A lot of problems arise from using devices with small memory (e.g. laptops) with limited backing store, rather than desktop machines with much larger storage. The assumption that cloud storage of any form will work as a suitable backup is just something I can't take.

Best to always back things up, and not necessarily rely on Time Machine either I think.

[Dave2002]

I noticed recently that my available space now only includes a very small amount of purgeable space, so presumably those files which Apple thinks I can recover again have gone. I have no idea what they might be, or if might want them again. If they are due to updates/upgrades, then I probably don't want them and there's no worries, but if Apple has been deleting music files which I might not be able to recover, then that's rather poor - as I mentioned earlier.

I also have a suspicion - though no more than that yet - that if anything involving purgeable files is invoked, that the MBP slows down drastically. A recent update took "almost forever", and that might have been when space was reclaimed. If that is the case, then it would be better to take manual action to clear out more space before any significant system updates or OS upgrades.

Is anyone else keeping an eye on this feature?

[MrGongGong]

Best to always back things up, and not necessarily rely on Time Machine either I think.

Time Machine is unreliable
My strong advice would be NOT to use it at all
I've had two instances where it completely corrupted all the data on the backup drives it was on and told me to reformat them

Cloned copy is the way to go in my experience

[Dave2002]

Time Machine is unreliable
My strong advice would be NOT to use it at all
I've had two instances where it completely corrupted all the data on the backup drives it was on and told me to reformat them

Cloned copy is the way to go in my experience

Couldn't clone software also fail? I haven't had the really bad experiences with TM you mention,
though some data may have disappeared which I didn't want to lose. I tend to have a haphazard approach to copying, so files that I really want to keep get backed up on multiple drives. It's inconsistent I know, but for the most part I've not lost much that I know of - though I did have a close call with one set of photos. I do have perhaps 30 Tbytes of storage to play with across different drives. Some people try RAID drives - but even then I think it's possible to have failures.

I read recently about the cost of storing commercial (including digital!) films - though the article was a few years old. The claim was that it was actually cheaper to keep film (i.e. analogue film) copies rather than digital copies. I think that things have moved on a bit since then, but amazingly some digital films were actually being converted to 3 x black and white films (for R,G,B I guess - or one of the other colour triples) and stored as film, as the thinking was that it would be cheaper for long term storage. For blockbuster films the studios are presumably prepared to pay really quite huge amounts to make sure they don't lose all their good copies. I think the figures ran into $10k or more per year for a 2 hour length feature film, and a studio which is trying to keep a lot of films archived would have to pay out quite a lot each year. Most cinemas are now digital, but the file sizes for a high quality digital film are very large - and I think just one film would use up all of my 30 Tbytes.

[MrGongGong]

Couldn't clone software also fail? I haven't had the really bad experiences with TM you mention,
though some data may have disappeared which I didn't want to lose. I tend to have a haphazard approach to copying, so files that I really want to keep get backed up on multiple drives. It's inconsistent I know, but for the most part I've not lost much that I know of - though I did have a close call with one set of photos. I do have perhaps 30 Tbytes of storage to play with across different drives. Some people try RAID drives - but even then I think it's possible to have failures.

I read recently about the cost of storing commercial (including digital!) films - though the article was a few years old. The claim was that it was actually cheaper to keep film (i.e. analogue film) copies rather than digital copies. I think that things have moved on a bit since then, but amazingly some digital films were actually being converted to 3 x black and white films (for R,G,B I guess - or one of the other colour triples) and stored as film, as the thinking was that it would be cheaper for long term storage. For blockbuster films the studios are presumably prepared to pay really quite huge amounts to make sure they don't lose all their good copies. I think the figures ran into $10k or more per year for a 2 hour length feature film, and a studio which is trying to keep a lot of films archived would have to pay out quite a lot each year. Most cinemas are now digital, but the file sizes for a high quality digital film are very large - and I think just one film would use up all of my 30 Tbytes.

Yes, ALL technology will fail
that's inevitable
BUT Time Machine is (and in all the studios and geeky places I go I don't find many folks using it) is particularly prone to sudden death at the critical moment.