On his Eclectic Light blog, Howard Oakley made the following comment in response to a comment on one of his articles:
TMH is on its way out, and has been replaced by TMA, which is better in almost every respect. I strongly encourage those using Big Sur and Monterey to start new TMA backups, not to continue using their fragile old HFS+ backups. At some time in the future, TM will stop backing up to HFS+.
(In context, I believe “TMH” refers to Time Machine → HFS+, and “TMA” refers to Time Machine → APFS.)
In my particular case, I have a 3TB USB 3.0 WD drive that I’ve been using since 2012, which is now backing up the internal SSD in my MBP (1TB). It’s essentially full (200GB of headroom, I assume maintained by TM), and the backup sets go back nine months. It is “Mac OS Extended (Journaled),” which I assume is the same as HFS+. I don’t really have any complaints about performance (of course, faster is always better), but I would like to have more than nine months’ backup history.
So, given Howard’s advice, my question for this forum is: What are the pros and cons of restarting my TM backup? If the recommendation is to do so, should I buy a new drive for this purpose (maybe larger, or faster, or maybe SSD vs. rotating), or just reformat my existing drive as APFS?
Con: you lose your Time Machine history
Con: APFS does not perform great on spinning hard disks. Firing off those snapshots to your APFS-formatted backup drive is going to get progressively slower. APFS is really designed to be used on an SSD, so if you can find a reasonably priced device I’d use that instead.
Pro: As Howard points out, and has written on extensively, TMA backups are just much better in every way. TMH, and its fragile house of hard links has always been a major point of failure for Time Machine backups. It’s honestly a miracle that it has worked as well as it has.
And as your 3TB drive is getting pretty old, I wouldn’t trust it with anything important going forward. Most spinning HDs are ticking time bombs after about 4-5 years. If you can spare the money, I’d replace it with an SSD that you could dedicate to TM.
200GB free on a 3TB HDD is near nothing. Go ahead and get a new disk, format it as APFS, and use that. You can always connect your old TM disk if you need to access your history. The new disk will allow you to use modern TM (TMA) and exploit its benefits. Disks are cheap. IMHO it just makes no sense to skimp on backing up. Also, with malware and ransomware, having a backup that’s not constantly connected is a good thing too.
On performance, while it’s true APFS performs better on SSDs than HDDs, the effect is most pronounced on disks that see many read/writes, especially rewrites. So the primary worry is boot disks or work/scratch disks. OTOH, a large empty disk that you simply back up to with TM until it fills up, is not that. It gets written to few times and then (ideally) goes to storage. If TM takes 70 sec instead of of 60 sec for a simple hourly backup, nobody really cares. And if you think you really do, well then shell out for an SSD. But HFS+ for TM should nowadays for most practical considerations be considered dead (or at the very least EOL’ed). The writing’s on the wall. And Howard Oakley is, as usual, right on the money with his advice.
In theory, if you “retire” your current hard disk TMH, you can always access it later on to look for old files. In practice the hard disk is likely to fail eventually (particularly if it is not used regularly). Also it is likely that future macOS will not be able to read old TM formats.
My strategy is to have several TM backup disks, including SSDs, with at least one stored “off site” (in my car).
I also use Carbon Copy from time to time in case I have a system crash (I intend to keep using Mojave!).
Finally I use 25 or 50Gb Bluray disks for really important data backup.
That reminds me - it’s time to do those backups
I would definitely quit using a drive that old. My process is to use a drive with Time Machine until it gets close to full then “retire” it and store it away in my fireproof file cabinet. I keep CCC backups in addition to TM.
I do the exact same thing. I buy a new SSD every once in a while, have TM fill it up to ~85%, then I store it in a safe offsite place and buy a new SSD for TM to continue on. Works great. Costs a little bit extra, but IMHO the added peace of mind is fully worth it.
Thanks all for the great info. I decided to go ahead and get a new 6TB WD drive ($100 on sale at Amazon). First TM backup is close to finishing; looks like it’s going to back up ~650GB in about 2.5 hours.
The weird thing is when I formatted the drive (with the GUI Disk Utility tool), I would have sworn I chose “APFS” from the several options listed, but I just checked and the Finder reports its format as “APFS (Case-sensitive)”. I specifically remember choosing plain APFS over that option, but who knows, maybe I fat-fingered it or something. Anyway, I don’t know what the implications of that format are (my internal SSD which is being backed up is plain “APFS”). Clearly if I need to re-format the drive, this is the time to do it. Any thoughts appreciated.
Thank you David (@davbro) and David (@Shamino). That article explains two things: Why I now have a case-sensitive container, and why I have a container with the " 1" suffix (which I didn’t mention in my post). OK, so TM is apparently doing what it will with my target volume, but also I (apparently) don’t need to fret. Another case of Apple Knows Best…pay no attention to the man behind the curtain.
My understanding is that SSDs need to be powered up once in a while to keep them working (i.e. storing data). That was a few years ago when they first became popular and I was looking at switching to them but it is worth checking on their potential storage life.
Wear is still the biggest factor for an SSD and in terms of that, a TM disk that gets written to essentially once is probably one of the most benign cases you could image.
