I know this has been asked before at various times but I want to ask it again just to bring it up to the present. I’m planning on buying an external backup drive, preferably SSD, for use with a new iMac. I will use this to make weekly backups rather than Time Machine updates so it’s going to get relatively little use. On my old iMac I have been using a couple of Samsung T5s for years, 1 GB capacity each. For the current machine, I was looking at either a T7 or a T9, also 1 GB capacity (the internal drive on the iMac is 1 GB). The drives are not that dissimilar in price so I may go with the faster device, which also seems to have better heat dissipation. My question is simply, Is there any reason not to choose one of these drives? I looked at the hardware on OWC’s site. Looks good but their SSD drives are easily twice the price for similar capacity. Faster but I’m just using them for backup. Probably with SuperDuper.
Two quick comments, keeping in mind I don’t know anything about the data and software you’re backing up:
- If you maintain two backups, with each backup made with a different backup utility, your choice of drives becomes less critical because it is unlikely both will fail simultaneously.
- I would buy backup drives with at least 50% more capacity than the device getting backed up. This is because, essentially, SSD memory cells can only be erased and written to a finite number of times. Keeping a generous margin of “open space” will help ensure you can make error-free backups and, most importantly, access your backups in a crisis.
Thanks. Well, I’m backing up my Tahoe machine, which means I’ll probably only be backing up user data. On my older iMac, after ofter ten years of use, the entire install amounted to about 180GB of data. Current machine has about the same. That will grow but probably not by much. My work is largely text based, so files are small. Even a 1TB drive will hold five times of my current dataset. I’d have to buy a 2TB drive to go larger.
There’s also the question of cost. I would like to buy a second external drive somewhere down the line, just for security, but can’t do it now.
Given your data usage and the shocking increase in SSD prices I would think about this:
I would seriously think about two of them which you could swap every week. Two is always better than one for back-up. 
Given the majority of your work is text based there is simply no need for the speed of an SSD. (It’s just fun to see how fast it is.)
Dave
For backup you don’t need a fast SSD. Of your suggestions (T9 and T7), the T9 is no faster. Both are 10 Gbit/s drives (with macOS) - get a basic T7 (or a T5 if you can still find one).
And I would use Time Machine, but if you want something else…
If the budget is tight, and the purpose really is just to backup around 200 GB, I’d give some thought to getting traditional external hard drives. They are slower and noisier than SSDs, but they are around half the price, especially with larger capacities.
For a complete backup system, you could get two 1-2 TB hard drives for not muc/h more than a single 1 TB T7, and rotate backup drives or use one as a Time Machine drive and the other for drive snapshots your favorite backup tool.
A basic 2 TB external hard drive from either WD or Seagate will run around $150 and be more than adequate.
SSDs are more expensive, but they’re more reliable and they are low power, hassle free, and silent. I’d get them for that alone, not the performance aspect. At least as long as you’re not in need of many-TB archival where the cost becomes prohibitive.
Since this is backup you’re talking about, a low-end but still reliable SSD would be my choice. If you put it in a USB-C (3.x) case rather USB4/TB4 you can save ~ $20, but on macOS that means you do lose SMART.
1TB Crucial is $159. (2TB is $265).
Here’s a USB4/TB4 case for $40. Getting the stick into the case takes about 10 sec and anybody, I mean really absolutely anybody, can do it. We use several of this exact model in our labs, no problems.
Here’s a $31 alternative.
And this is the USB 3.1 alternative for $16.
I will echo what some others have said: do not spec capacity too tight. You always want room left over for the drive and the file system to work well. And you don’t want to limit your backups just because you’re running out of room. But I will, just for sake of completeness, also caution against vastly over-specing capacity too — the capacity you buy today that only ends up being used many years later, is capacity you likely bought at far too high cost. Apart from this little AI fueled cost bubble we’ve seen over the last 12 or so months, storage capacity has always become significantly cheaper over the course of several years. It’s usually far cheaper to add modest amounts of storage to your backup disk series over the years, than today buy one huge drive that is supposed to last you for a decade plus.
Thanks. Very helpful information. Yes, I like SSDs because they are quiet, simple, bus-powered, and portable. (I’m also shocked by the rapid cost run-up of SSDs over the past year.) I’ve assembled several external hard drive units over the years and rebuilt a couple of old Intel PCs in the distant past. I don’t find the assembly part daunting.
Prices are $240 for the T9 and $220 for the T7 (both 1 GB capacity). According to the blurb on Amazon, the T7 is 1050 MB/s and the T9 is 2000 MB/s, so roughly twice as fast.
I’m afraid you won’t see any of that on a Mac. The 2GB/s figure is crediting USB 3.2’s 20 Gbps mode, but Macs do not support that.
On a Mac, it’s either 40 Gbps on TB4/USB4 or 10 Gbps over USB3. If you get a TB4/USB4 enclosure like I linked to above, you’ll see >1 GB/s from any decent NVMe stick. Otherwise, you’ll be capped by USB3 at somewhere around 900 MB/s. For regular backup tasks that’s obviously fine. It’s the initial huge write or the restore from backup where you’ll notice the higher throughput. For incremental backups, it’s not really a factor. And with TM not at all since macOS limits TM’s i/o bandwidth to ~ 300 MB/s peak even with the fastest sticks on TB4.
Oh, didn’t know that. Well, there are four TB4 ports on the back, so if I can get 1 GB/s that would be reasonable. The initial backup may take a bit of time but that’s understandable and acceptable. I’m curious, are there external SSDs that provide that higher 40 Gbps (that’s Gbps not GBps?) throughput? I recall seeing some hardware from OWC that could do that.
Absolutely. But they’re expensive. This Samsung is $383 for 2TB, but it will fully saturate TB4’s 40 Gbps.
Thanks. Yes, this one’s a bit more expensive. Nice piece of hardware though.
If you build your own external drives, there are quite a lot of TB4 enclosures to choose from. But the least expensive ones start at around $50 (compared to $10-15 for a USB3 enclosure).
If you cared to read the thread, you’d see that I already linked to 2 that are well below $50. And, as I wrote above, you save about $20 (but lose SMART) by going for cheaper USB3 enclosures. Reading > posting.
The MAIWO looks very nice. I’ll probably go with that enclosure.
MAIWO is the enclosure brand I bought, only to return it because it caused immediate kernel panics on one Mac and didn’t mount on the other.
What kind of SSD was inside?
M.2 PCIe Gen 3.0 x4 NVMe SSD (Western Digital PC SN720 SDAPNTW-512G-1006)
I also use an M.2 SSD and enclosure for backup purposes. I have partitioned a 2Tb SSD - one for Time Machine and the other for bits and pieces such as Calendar and Contacts archives plus photos and videos that aren’t needed on the Macbook Air main storage (500Gb).
As a rough rule I prefer a Time Machine drive to have twice the capacity of the Mac.