Recommendations For New SSDs?

For externals…either the Samsung T5 or T7 series if you need something really small. If you aren’t traveling with them then I would get an OWC external SSD…there are several models to choose from from small to a bit larger but with fins to help with cooling.

I have the Samsung T7s for traveling and my Intel iMac boots from one of the OWC ones (macsales.com)

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Without hesitation, Samsung’s 2TB SSD model Portable T7. I have two which I use for backups. They are the size of a credit card and perform flawlessly. Best, REShaman

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This combo is inexpensive ($198 shipped) and doesn’t even require screwdriver.

You could shave off $15 by going SanDisk instead of Samsung. Personally, I prefer the latter but the former should be OK too.

You’d probably want a PCIe-based SSD in a TB3 case for performance reasons if this were a disk you’d be using for actual work (or boot), but since it’s for TM, SATA-based is perfectly adequate and a lot less expensive ($130 less in this example).

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Getting an external SSD to use for a versioned backup (e.g. Time Machine) can end up being A HORRIBLE IDEA!

While using an SSD for a clone backup (e.g. Carbon Copy Cloner or SuperDuper!) is a very good idea…

(see Lesson #1)

because of the nature of Time Machine ™, it plays right to the weaknesses of external SSD’s.

External hard drive manufacturers for some reason think of all external SSD’s as portable drives. I’ve yet to find an external SSD that is robustly designed. Cooling tends to be so bad that even though external SSD’s often are blazingly fast, they tend to quickly overheat and then throttle back precipitously.

How fast SSDs slow to a crawl: thermal throttling

Safe SSD Operating Temperature: Is Your SSD Running Too Hot?

This is especially a problem when backing up using TM, because TM backups can really exercise a hard drive.

But that isn’t the only problem SSD’s have when used for Time Machine backups. TM works by keeping versions of all of your past files, quickly filling up your hard drive. Once your hard drive is filled up, TM is designed to started deleting the oldest files to make room for new files. The problem is that SSD’s start drastically slowing down when they get about 70% full. So, after that, your TM backup will become molasses slow, and even possibly fail.

"The rule of thumb to keep SSDs at top speeds is to never completely fill them up. To avoid performance issues, you should never use more than 70% of its total capacity.

“When you’re getting close to the 70% threshold, you should consider upgrading your computer’s SSD with a larger drive.”

“SSDs may suffer performance issues, especially in writing speed, when the drive reaches full capacity. It is easier for the drive to write to an empty cell when there is free space available. When the drive is full, the SSD needs to find out which blocks are partially filled, move that information into a cache and then write it back to the drive. It is best to have 10-15% of your drive set aside for free space, to keep a good balance between performance and space utilization."


Randy B. Singer
Co-author of The Macintosh Bible (4th, 5th, and 6th editions)
Macintosh Routine Maintenance • Macintosh Routine Maintenance


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Overheating can be an issue on PCI-e based SSDs that push serious data rates (2 GB/s and beyond). SATA-based SSDs that hit ~500 MB/s, can sometimes get warm, but are rarely found to get hot let alone overheat. That is why all these discussions about throttling and actively cooled cases (fan) usually pertain to more expensive NVMe based SSDs, just like the Samsung X5 in Howard’s article you quoted above. If you get a standard SATA SSD (like a Samsung 870 QVO) and you slap it into a cheap plastic case, it wil get warm when you put it under sustained load, but you’ll never find it too hot to touch no matter how much you thrash it. It’s simply not fast enough. And such drives are just fine for TM (provided you stick to the cardinal rule to swap them once they reach ~80% of their capacity—same as for HDDs btw).

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I just updated my 2018 Mac mini external data drive from 10 TB HDD to a 4 TB Samsung Evo that I put in my OWC external box. It is working very nicely. I use the the other 10 TB HDD for Carbon Copy Cloner. I like Samsung EVO SSDs. I wouldn’t get a QVO as they are slower and don’t last as long. We replaced a 128 GB SSD on our 2015 MBP with a 1 TB internally but that might be out of your comfort level. The T5/T7 SSD external little drives are a favorite of mine but I think they top out at 1 TB, not 2.

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I’m not too surprised. I’ve found that most external drive enclosures have pretty poor cooling. Most are plain aluminum (or worse, plastic) cases without fans. They rely on conduction (if the top of the drive can contact the enclosure, hopefully via a thermal pad), but that is often not enough to keep a drive cool.

These enclosures are fine for drives that experience occasional use, but they’re terrible for something you will be using for extended periods of time (like the target of an hourly backup solution).

Enclosures with fans can be purchased (and I recommend them), but they are definitely in the minority.

I think the same should apply if you are putting an SSD (of any form factor) into an external enclosure. Look for a case with a good thermal solution, including heat sinks and/or fans, even if it ends up not being the smallest or most portable device.

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I’m not convinced that this is necessarily the case for Time Machine. Especially if your TM volume is formatted for APFS.

The reason is that TM volumes don’t experience random write/erase operations. For each backup, new snapshots are made, and these snapshots are read-only. The disk blocks used by those snapshots don’t get freed until all the snapshots pointing at that block get freed, which may not be the case for a very long time.

In general, you’re going to find the TM volume using new disk blocks, with very little blocks being freed until the volume fills up. And then, it will be done a snapshot at a time. This is a very different usage pattern compared to (for example) your home directory, where files are modified and deleted all the time.

A rule of thumb like never exceeding 70% capacity, while perfectly reasonable for a working drive, may not be valid for a backup device that uses snapshots for keeping historic backups. Maybe it will prove to be the same, but I think that needs to be tested before you can claim it to be true.

Of course, all such wear-leveling issues can be significantly aggravated if your device doesn’t support TRIM (which I think will be the case for any USB drive, but maybe not for a Thunderbolt drive).

(And I personally have no problem with using hard drives for backup devices, and this problem won’t be applicable to them.)

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Actually it can be very simple via OWC. You can buy just the enclosures or your choice of enclosure and an appropriate size drive. Check out the myriad of options here. Here is a link for SSDs

I use a SanDisk Extreme Pro v2 SSD for CCC backup, and it works great. I like that the backup runs are extremely fast - typically under two minutes - and I can back up my Mac on the go. The speed actually helps me to be more diligent about running the backup jobs frequently. The Pro version SSD gets warm but is good at dissipating heat due to its aluminium enclosure.

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A number of responses:

I’m already hearing from folks who say that their TM drive fills up, and then stops doing backups. I haven’t heard of any other explanations for this.

You can get a huge SSD to work around the problem of the drive filling up, but the price of huge SSD’s is silly compared to similarly large RDHD’s.

I don’t know of any external SSD’s that use Apple’s implementation of TRIM. They may do some TRIM-like things based in their own ROM, but it’s not like having a full implementation of TRIM enabled.

Note that Samsung’s SSD’s are very popular because of their price and initial performance. But they tend to slow down early in their lifespan and have no over-provisioning whatsoever. Tradeoffs for the low buy-in price.

Lots of folks think of SSD’s as being magical devices that are always fast and which are ultra reliable. Unless you purchase an extremely well made one (which will noticably be priced to reflect this), like many Intel models, you can bet that your SSD has had some corners cut to be reasonably priced. That will likely come to haunt you at some point.

There are external case kits, and I’ve considered building my own external SSD myself. Note that what you are looking for is a case kit that includes a very robust power supply, and a fan. To my knowledge, this doesn’t describe any case kits from OWC. In fact, when you find these rare case kits, they will be surprisingly expensive. Note that external case kits with aluminum cases (supposedly used as heat sinks) aren’t doing much unless the hot parts of the internal mechanism are in physical contact with the external case. It is extremely rare to find an aluminum case kit where this is actually how things are mounted.

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Off the topic of SSDs but just for information…
In November, I purchased a Toshiba N300 4TB HDD and a Vantec Nexstar enclosure and configured it as my Time Machine. It gave a number of intermittent problems including randomly ejecting itself and only showing the last 24 hours of backups when I entered Time Machine. It was also surprisingly noisy. I wasn’t sure the problem was in the HDD so first I replaced the cable then the Vantec but the problems persisted. Finally, I replaced the Toshiba with a WD Blue 4TB HDD and that has run smoothly and quietly. I’ll wait a few days before returning the Toshiba (suitably erased) to Amazon.
The WD Blue is 5400 rpm but I can’t say that it makes any difference so far as Time Machine is concerned.

On the topic of WD HDDs, back when I used HDDs a lot I was pretty much always happy with WD drives. At work we usually had the Black series (or Red for network storage) and for TM at home where I was more concerned with noise/wattage than with performance I usually went with Green. In all the many years I went through about 30 of these disks and I never once had trouble with any of them. Most I still have around to this day stored way in case I ever need to access their backup data. I did have one DOA (a Green 1 TB in ~2015) that was promptly exchanged with the replacement being flawless. I would without hesitation get a WD again if I were still buying HDDs. Fortunately, my personal needs these days are well served below 4TB which means SSDs are affordable, so I’m not planning on buying a HDD again any time soon.

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I’m also using an N300 drive. It is noisy - you can’t miss its head motion noises. It also runs warm - in part due to its being 7200 RPM.

You didn’t say which NexStar enclosure you’re using. When I was using a TX enclosure (no fan) with my TM drive, I saw the same flaky behavior after a month or so of usage. When I swapped the case to an HX enclosure (with a fan), the problems went away.

I don’t have a particular problem with WD drives, but do read the specs. I personally would use a Red Pro or Gold drive - they are 7200 RPM, use CMR and are rated for 24x7 operation. I would be much less inclined to use a Blue, Green or Black drive.

David,
It’s the HX enclosure. I’m sure you are correct about the quality of various WD drives. I chose the Blue for two reasons (1) it was cheap and (2) it was in stock at my local BestBuy. Frankly I bought it just to see if the problems I was having were with the Toshiba or elsewhere. Having exactly the same hardware except swapping the Toshiba for the WD resolved the problems (so far). The WD Blue was cheap enough that I won’t feel bad about moving up to one you recommended.

Interesting. I’m assuming you mean the current model HX (link). There were three prior discontinued enclosures that also have the HX name (but they all have fans as well, so maybe it doesn’t matter that much).

It sounds like you may have had a bad drive. The only other thing I could think of would be to make sure the fan is actually turned on. There’s a rotary switch below the power switch that turns the fan on/off and controls its speed. On mine, the fan is always running at its maximum speed.

Either way, if you’ve got something that works well for you, that’s what matters.

Yes, current model. Agree it’s probably a bad drive. As I wrote, if the WD Blue runs without problems for a week or two I’ll erase the Toshiba and return it. Anyway, interesting though this is it’s off topic for MMTalker who asked about SSDs.
I have used several SSDs and have been more than satisfied with a SAMSUNG 860 QVO and a Crucial X6. Both are 1TB but I’d expect the 2TB versions to be equally satisfactory although much more expensive.

I think this is very interesting, and I’ve learned a lot about the different types of removable drives.

You are most welcome. Learning is the great value of this community.
I would point out that this discussion covered two major topics (a) solid-state drives (SSDs) vs. rotating ‘hard’ disks (HDDs) and (b) putting together your own external drive from separate parts (drive+enclosure) vs. buying the finished thing. The choice you make on (a) depends on what you will use the drive for and your budget.
The choice on (b) depends on your level of technical confidence and your budget. Actually, building your own is a trivial exercise, all you do is plug the drive into the enclosure and tighten a few screws. While you do save some money the real benefit is that you choose exactly which model and specification of drive that best suits you, otherwise you are buying a black box, literally.
Good luck!

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I respectfully disagree with @MMTalker about needing speed. Backup is by definition a background task, archiving even more so a task that only occurs occasionally.
Far more important is long term reliability.

SSD can be as reliable as HDD, but they come at a cost.

Proper reliable drives can’t be found amongst consumer drives, we need to look at enterprise drives, we can recognise them by the warranty they give, consumer typically up to 2 years, enterprise commonly 5 years. Experts looks at MTBF and many other reliability factors from the data sheet. Reliability also means looking at 3.5" drives. @MMTalker doesn’t want to build her own drive, enterprise drives in an external enclosure from the shelf are to my knowledge non-existent.

As an example I name Seagate Exos E series, admittedly not for @MMTalker, given the stated requirement for a finished product.