External storage for the new M1 iMac?
May 1, 2021 12:07 AM   Subscribe

I am on the verge of buying a new M1 iMac, with a base 256Gb of storage. As the Apple storage upgrades are absurdly overpriced, would it be an option to connect an external SSD (via Thunderbolt?) without a loss of performance?

The base model of the M1 iMac has a 256Gb hard drive, which is comically small these days. But an upgrade to a 2Tb drive is something like $800(!). I can get an external 2Tb drive for a quarter of that price. So if I just have the 256Gb, then have the 2Tb external--would that be do-able? Would I need any other hardware besides just a Thunderbolt cable? Is there anything particular with the M1 Macs that an Apple hard drive is preferable?

And I will just splurge on the 16Gb RAM; it's "only" $200, but aside from cracking the thing open (assuming that's even possible), there's no way to upgrade RAM myself. But the hard drive? I'm thinking an external drive is an option, and if it is that'll save quite a bit of cash. Also, I will use an external 2TB HDD for backup in any event, external main storage or not.
posted by zardoz to Computers & Internet (15 answers total) 5 users marked this as a favorite
 
Best answer: Well the internal SSD is "up to 3.4 GB/s". I can't find any external SSDs that are that fast, but how much slower they are depends a lot on how cheap they are - the $200 ones deliver more like "up to 540 MB/s". Just to be clear though, the Apple upgrade isn't so expensive because you're getting a crazy-fast drive, that's just Apple Tax. The speed difference is largely due to external bus (TB3) limitations, and for computers that support NVMe Gen4, $350 will get you 2TB of storage that go "up to 7 GB/s".

How much raw disk throughput will meaningfully affect your experience depends entirely on the kinds of things you'll be doing with the computer. Maybe you can get away with 256GB of speed critical stuff and use a slower SSD for stuff like media where you don't need to read the entirety of a big file all at once. If you do get an external drive, it'll almost certainly come with a suitable cable.
posted by aubilenon at 12:51 AM on May 1


Response by poster: aubilenon-thanks, and to follow up on "The speed difference is largely due to external bus (TB3) limitations, and for computers that support NVMe Gen4, $350 will get you 2TB of storage"...does the M1 iMac support NVME Gen4? I'm new to this term and am researching it now.
posted by zardoz at 1:06 AM on May 1


Best answer: Thunderbolt 3 is 40 gigabits per second which translates to 4 giga bytes per second due to 8 out of 10 bits being data and 2 in 10 being error correction[1]. The kind of NVMe drive you'd consider would be PCI-Express in 4-lane configuration, so maximum of 3948 megabytes per second for PCIe 3.0 or 7896 for PCIe 4.0 [2] -- while even the fastest PCIe 4.0 drives don't sustain their peak speeds, reaching around 3000 megabytes per second due to a combination of caching and cutting back speed to avoid overheating.

So pick a good PCIe 3.0 NVMe stick, a solid Thunderbolt 3 enclosure -- and make sure it has two ports for daisy-chaining more Thinderbolt devices -- and accept that's the best you can add to the M1 Macintoshes.

NVMe sticks include the Samsung 970 Pro or 970 Evo Plus (a value proposition of PCIe 3.0 getting you more storage space) and the WD Black SM850 (a PCIe 4.0 device). Enclosures with 2 TB3 ports include the OWC Express 4M2 and Lacie Bolt 3.

1: https://en.wikipedia.org/wiki/8b/10b_encoding
2: https://en.wikipedia.org/wiki/PCI_Express
posted by k3ninho at 5:57 AM on May 1 [1 favorite]


As you rightly point out that internal storage is a joke. From my experience of MacOS, once that disk is around 200GB full, you'll probably start taking a performance hit. Remember SSDs really like/need lots of free space to allow the disk controller perform essential house-keeping tasks.

BTW, seriously re-think about an external storage as your main disk if you have kids / co-workers in your house / workspace. Because, if somebody disconnects the disk running your operating system (when switched on) from your iMac, you could end up with some serious corruption and data loss.

Likewise, if your house or office is subject to a burglary, slipping an external SSD disk in their pocket is easily done. No so, for a whole iMac system! So if data security or confidentiality is an issue - this is another factor to consider.
posted by jacobean at 6:16 AM on May 1


Likewise, if your house or office is subject to a burglary, slipping an external SSD disk in their pocket is easily done.

On the other hand it’s easier to hide an external SSD rather than an entire iMac if you wanted to hide your important data somewhere while you were away for a period of time, for example.

I think one thing to bear in mind is how you would organise data across two drives. You could put your entire user folder on the external drive (for example, although that’s just a random Google result). But maybe keep a separate admin user who has their user folder on the iMac still - I’m not sure if you could move the only user folder to an external drive.

Or, if you don’t generally have a lot of documents but you have a massive Music library, or a massive Lightroom photo library, or loads of movies, etc, you could just keep that on the external drive.

I usually spring for a big internal drive because it’s so much simpler to manage, and less to potentially go wrong. But, like you, the prices now would give me pause.
posted by fabius at 6:29 AM on May 1


Best answer: I know this is going to be painful... but I would buy the internal storage. Depending on what you do, I might even try 8gb of ram and big storage and test it out (within the 14 day free return period, of course). You can always wait a few minutes during a project for slower compute - but you cannot "wait" and get more storage.

I have used macs in professional and production environments since 1996. As frustrated as I am with modern Apple's lack of expandability and repairability... the soldered-on storage and RAM has made these machines so so reliable. Like bulletproof, run for years without a single issue. I've gotten 10 years minimum use out of each Mac I have owned since 1996 so the value over time has been really really good. I now treat macs as an appliance - specced out for each purpose and when they no longer fit the task, they are sold or traded in for their high resale value.

The only use case I would support for external storage would be something with large files that are completely separate from the OS and normal functioning of the computer. For example - you use Adobe Premiere for video and you keep all your video and media on the external drive.

I would not put mac OS on an external anymore (I have with disastrous results), nor would I put anything that the OS might expect to sync to the network: a home folder, or an apple Photos library, apple Music library or any folder with a syncing service dropbox, iCloud drive, Google Drive (though I have in the past, again disaster).

Fast external storage is out there - but 2gb at close to 2800 MB/s is almost $500. for $300 more you could get it internal and not have to worry about it.
posted by sol at 7:02 AM on May 1 [4 favorites]


Enclosures with 2 TB3 ports include the OWC Express 4M2 and Lacie Bolt 3

These boast up to 2-2.8 GB/s. If you’re capping out at that speed why not just get a regular external hard drive with that speed, and save a couple hundred bucks and some fuss?

To answer the op’s follow up question, the 2014 Mac mini is the last one to feature upgradable internal storage.

The big question is what kind of stuff are you gonna fill the bulk of your 2tb with? If it’s media then you might be fine with a slow-ass $60 spinning rust hard drive, as you don’t normally need to read an entire blu-ray rip in like 15 seconds.
posted by aubilenon at 7:08 AM on May 1


The key here is that a M1 iMac offers no internal upgrade possibilities after purchase.

OWC offers internal storage upgrades on (intel) iMacs. Instruction videos are available... None of this applies to the M1 iMacs.
posted by blob at 7:39 AM on May 1


I know the upgrades are expensive but I absolutely URGE you to not buy 256GB of internal storage if you plan to keep this machine for a long time. You don't have to go all the way to 2TB, but I'd do at least 512GB. I agree with Sol, that you do not want to boot from an external drive, and there are things that "expect" to be on the boot drive. Yes, in most cases there are workarounds, but you are signing yourself up for years of headaches and potentially breaking workarounds if you have internal storage that is too small. And as mentioned, SSDs need a decent amount of free space in order to perform well. Buying the smallest internal storage for a long-term machine is penny wise and pound foolish, IMHO.

External SSD are quite usable, and I use a couple myself on my own iMac. I just don't use them for the OS or stuff that's tightly-coupled with the OS.

Get a big enough internal drive for your main stuff, and use external drives if needed for projects, assets, archives, etc.
posted by primethyme at 8:38 AM on May 1 [4 favorites]


I find I get spinning colorballs on my Mac if I ever dip below about 20 GB of internal hard drive space. On a 256 GB drive, that's nearly 10% of the space. I agree with primethyme, at least get 512 GB. Honestly I'm wishing I went to 1 TB when I bought this machine in 2019.
posted by praemunire at 8:59 AM on May 1


I have no personal experience with this, but this article might be worth a read: https://www.zdnet.com/google-amp/article/losing-the-apple-storage-tax-on-m1-macs/
posted by majikstreet at 9:38 AM on May 1


Best answer: You might want to consider the speed you need, rather than the speed you could have, on that external drive.

I use a usb-c (not thunderbolt) ssd (500GB, around 500MB/s, I think, not offensively priced and smaller than a wallet) for time machine backups and literally never notice when the backup happens. Similarly, if you were storing your documents on the drive, or modestly sized programs (probably not games with a ton of media) I think it would be fine. You might notice more lag with a photo library, but I think it would still be adequate.

Your internal media will likely always be the fastest you can get, but 500MB/s is still maybe 5x what spinning disks get (with lower latency to boot, so it feels faster still), 5x the max you would ever see for a network drive, and 20-50x what standard cheap USB sticks achieve, so is probably faster than you're used to experiencing from external systems.
posted by How much is that froggie in the window at 9:58 AM on May 1 [1 favorite]


Please get at least 512GB internal storage. I’m so glad it did when I bought my M1 MacBook Air. My everyday needs are just a little less than 256GB, and having a the extra space gives me loads of breathing room. For external I just have a spinning 2TB drive which is fine for what I need.

I wish I’d bought the 16 GB RAM as well… not that I have had any issues with 8GB, it would just make me feel a little better.
posted by lhauser at 12:37 PM on May 1


Response by poster: Thanks for the answers everyone. I made a mistake above--the base memory is 512Gb, not 256Gb--even Apple isn't that cheap. I plan to use a lot of disk space for video projects, so maybe I will splurge for the internal drive. Work is paying for it anyway, and it's a use it or lose it kind of thing, so I think I might use it. But there's a lot to chew on here, and lots of good options, it seems.
posted by zardoz at 2:11 PM on May 1


Actually, Apple IS that cheap. I have one. My local Costco had them on sale just when I was having serious issues with my lovely ancient mac pro, so I bought one. The specs are 8gb ram 256ssd. I bought an 8tb spinning disc for my storage needs (I save a lot of photos & music) It seems to be fine. I'm not sure what kind of speed intensive needs you have but I watched a lot of youtube vids that pointed me in the direction of these.
posted by evilDoug at 5:53 AM on May 2


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