External Desktop or Portable for back ups? HDD or SDD?

@JohnAtl - This is a good point. Our home Macs are desktops, for which the portable HDDs work perfectly. Backup considerations for MacBooks would be different.

Regarding the Backblaze drive stats - these are fascinating, but difficult to assess for our use case. Backblaze uses enterprise-class drives, helpfully listing the actual drive model numbers. I have drilled around on internet discussion forums and disk drive reviews, trying to correlate these drives with those actually available to purchase. There are those who claim that some desktop-type consumer drives (Seagate Backup Plus or WD My Book desktop-type drives) contain certain disk drives that are enterprise-type drives - WD Red, for example. Checking further, others state that the WD drive enclosures contain “white-label” drives that may or may not be the same drives used by Backblaze. By the time that the word got out that the WD My Book enclosures contained WD Red drives, the drives were changed to generic “white label” drives. Similar story for Seagate. Bottom line - I found the Backblaze reports interesting in a general way but was not able to use the Backblaze stats to purchase specific hardware for my use. I ended up using portable (2.5”) drives, anyway, so the Backblaze stats for 3.5” drives were not applicable.

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That’s exactly what I do. SSD for CCC clone, spinning drives for other backups.

I want multiple backups, using at least two different methods, with one or more copies offsite. Currently using CCC and Time Machine but testing Arq as an alternative.

Hard drives are cheap, my data isn’t.

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Their published data are expressed as an annualized failure rate, which accounts for number of drives in use. More at the link.

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My apologies. I was basing it on this comment from Rdddir:

TL,DR: Seagates are failing more because they have been used more, not because they’re less reliable.

Assuming all drives have data read/written to/from them at the same data per unit time rate (TB/year, for example), then you can use the Drive Days/Drive Count to approximate how much usage each drive has seen.

In other words, a drive with a low failure rate because it’s seen less usage isn’t necessarily more reliable than one that’s seen more usage; it’s just been lucky to have been through less.

Therefore, the only “bad” drives in this table are the ones with below average usage AND above average failure rate.

Simple Excel shows that the only drive that fails the above criteria in the Lifetime table is the Seagate Exos X 12 TB (ST12000NM0007), which might explain its shockingly low (for the specs) retail pricing.

In fact, 2 of the 3 drives with the highest usage are Seagates, and Seagate is the only brand with more than 1 model having a usage time exceeding typical enterprise warranty (5 years, or 1826 days).

Note that the equal workload assumption above may be incorrect, but since Backblaze doesn’t tell us which drives are assigned to which workloads it’s difficult to say with any certainty. Hopefully all the drives have the same workload, because if they don’t that would basically make comparison invalid (workload has no effect on drive reliability below the drive’s workload rating, but the effect increases linearly above that rating) without knowledge of HDD-workload pairing.

For example, if the Exos X 12 TB HDDs are being assigned to workloads 2X their rating, they’re gonna fail at a much higher rate than other HDDs assigned to workloads below their rating.

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You have gotten good advice here, and I can only second the points that have been made.

I personally prefer WD drives, but that’s purely because I have had a few failures with Seagate external drives. That’s not based on real science as the sample size is of course way too small.

For a desktop, I would strongly argue in for the much less expensive and higher capacity spinning hard drives for backups. Like others, I have two bus-powered drives velcro’d to the under side of my desk, one for TimeMachine and one for a CCC bootable clone. For backups of this sort, SSDs are in my opinion an unnecessary expense, especially if you are backing up a desktop where the time for the backup to take place is longer. If you are backing up a laptop that will only be able to be connected to the drive for a short period of time (as per @JohnAtl), then an SSD may be worth the added cost, especially as your internal drive is probably smaller and hence a smaller external SSD would suffice. I favor drives at least 2x the size of the internal drive for both TM and CCC, although I actually use a much larger one for CCC since these bus-powered drives can be purchased so cheaply on sale, and I don’t delete the “safety net” backups.

Externally powered drives are, I think, helpful if you need a faster drive rotational speed as some are 7200 RPM drives while the bus powered ones are pretty much all 5400 RPM, and again I don’t think the faster rotational speed is needed for backups.

It is a reasonable point that have an SSD based clone is useful if you ever have to run your computer booted off the clone, but that to me is a relatively unlikely scenario for most of us. If your internal drive died on laptop or desktop you would like be taking it in for repair/replacement and hence the clone wouldn’t be useful anyway, When the repair machine is to be restored, yes the clone process going back will take a bit longer, but it’s a one time event.

However, if you are, for instance, frequently traveling with your laptop and need to be assured that if your drive were to die while traveling you could continue to work with the speed of an SSD, that might be a use-case for an external SSD clone. For instance, when I give talks, I will often bring a bootable clone of my laptop so that if my drive dies in transit I will not be stuck. (I also bring a spare copy of the talk on a USB stick and I could also grab a copy from BackBlaze or from my home machine via ResilioSync, but since the rest of the world is so Window-centric I might not be able to find a spare Mac to load my Keynote file). Thankfully I have never had to run out to buy an emergency Mac to give a talk!

Long winded, but hopefully helpful.


Dredging up the Backblaze drive stats topic again …

Looking back over the Backblaze stats over 2-3 years, some of the most reliable drives have been HGST (now owned by WD, as pointed out by @JohnAtl), I was inclined to track down a source for these and buy a number of them (2 - 4) for a tentatively-planned Synology NAS. Easier said than done. First, availability is limited. Second, these drives tend to be expensive. Third, reviewers of these drives repeatedly mention the noise generated, especially if there are multiple drives. OK … I can be patient and wait to find 3 or 4 drives, and I could probably choke and suffer through the cost. But no way am I going to allow multiple noisy disk drives to run continuously in my small home office.

Lesson learned: disk drives that are appropriate for enterprise use may or may not be suitable for home use.

Yeah, it seems like when I looked for them they (HGST) were only available in Costco-sized bundles.
I wound up getting 4x4T WD Red NAS drives for my Synology.

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I’m jealous. Do they work well? Quiet?

Yes, they are quiet. Not silent. I’m easily annoyed by noises, and they don’t bother me.
I’ve had them since January of this year, and haven’t had any problems with them.
Looks like they are $24 cheaper than when I bought them.

I agree for Time Machine, but not for a bootable clone. When you’re backing up, using an SSD for you’re bootable clone may seem like an unnecessary expense. When the time comes that you actually have to boot from that “bootable” clone, it’s going to be sooooo slooooow. I’ve run a system from a bootable clone on a spinning hard disk and it is downright painful. If you actually have to use it, backing up to an SSD for a bootable clone is more than worth the additional cost.


My external 1TB USB Time Machine disk is getting full. What do you guys do to transfer them to another bigger USB disk? Or do you just plug that bigger drive in and backup as a NEW Time Machine drives?

Just remove the drive from backups and start a new one. Keep the old drive for a while if you want access the old versions and deleted files, but eventually you can wipe the old drive and repurpose or dispose.

In this case, when plugging new drive to Time Machine, it will ask if you want to Replace or Use Both drive. I suppose Use Both is the better response as I might need to recover older versions of certain documents from the old drives, right?

You could, but then the computer will start complaining that you haven’t backed up in X days, even if it has to the new drive.

You can leave it and always remove it from the list later if you want. Either way you can plug in the drive and browse the files by backup time in Finder when needed.

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I didn’t realize Use Both implies that I also have to backup to the old drive from time to time! I thought Use Both means I am keeping the old drive to be available for TM recovery via that “go back in time” Finder interface. Thanks for the tip!

@JKoopmans posted the answer to that on this thread:


I agree that if you are going to do any appreciable work off a bootable clone, having it on an SSD is going to be a necessity these days. Going back to a spinning hard drive would be torture!

That being said, I am good with a cheap spinning drive for my boot clone. If for some reason I actually had to work for any reasonable length of time off the clone I would most certainly clone it over to an SSD, but if I just want an emergency bootable disk and the ability to restore after getting a machine fixed if the internal SSD did not survive the repair, a spinning drive has me covered.

If all you’re going to do is restore off of it I’m not sure a bootable clone is the right tool. Something like a Time Machine backup would probably be fresher than a bootable clone.

In my case, the bootable clone was the fastest restore option. My 2011 MBP’s GPU died and it would not boot. Noticed this in the morning. I have CCC run a clone operation in the middle of the night. I was able to clone the backup to my wife’s old iMac that we hadn’t repurposed yet. Up and running in an hour or two. A time machine restore would probably take much longer.

I actually have both a clone and a TimeMachine drive hooked up to my iMac Pro. My view is that if I needed to restore the entire system, I would likely do so via the clone, but if I needed to retrieve a smaller subset of files I would turn to TM first.

The clone is updated daily and so it would only be slightly out of date compared to the TM backup, from which I could renew any recent work as well.

In reality, I would probably if faced with this issue build the new machine from scratch taking the opportunity to have an effective nuke and pave. Since all of my data sits on the external Drobo, bringing my data files back online is the easy part of this.

I keep the TM and clones (there’s also a daily clone to my backup Drobo) as well as BackBlaze and Arq, for security against data loss.