Which external SSD works best with Apple iMac M4?

> Since the M4 supports Thunderbolt 4, I want to make sure I’m getting something that actually hits those high transfer speeds without overheating. I’ve been looking at the Samsung T9 and the SanDisk Pro-G40...

Sooo I just found this thread and honestly, I am SO excited for you getting that M4 iMac!! It is such a beast! But yeah, 256GB is basically nothing when you're doing 4K video, so I totally feel u there.

For your situation, I would suggest looking at the SanDisk Professional PRO-G40 SSD 2TB over the T9. Basically, the T9 is great but it uses USB 3.2 Gen 2x2, which Macs (even the new M4) dont fully support at top speeds—you'll usually get stuck at around 1000MB/s. But the G40 is a literal tank because it has BOTH Thunderbolt 3 and USB 3.2 compatibility. It actually hits those 2700MB/s+ speeds on macOS Sequoia which is amazing for scrubbing through 4K timelines!!

Another reallyyy cool option if you wanna save some cash for extra gear is the OWC Envoy Pro FX 2TB Portable NVMe SSD. It is super rugged and works fantastic with the M4 chip's Thunderbolt architecture. It stays pretty cool too, which is huge cuz some of these drives get HOT when exporting long videos.

Basically, the SanDisk Professional PRO-G40 SSD 2TB is the premium choice for speed, while the OWC is just a solid, reliable workhorse. Both should be right around or under your $300 budget if you catch a sale! Hope that helps, good luck with the editing! peace

yo, congrats on the M4 iMac! i feel u on that 256GB struggle... apple really makes us pay for that internal storage lol. anyway, i've been doing 4K editing on an M-series chip for a while and the SSD choice is actually KINDA tricky cuz of how macOS handles different protocols.

Basically, the Samsung T9 Portable SSD 2TB is super popular but it uses USB 3.2 Gen 2x2. The problem is that Mac Thunderbolt 4 ports dont actually support that specific 20Gbps speed, so it'll usually drop down to like 10Gbps (around 900-1000MB/s). It's still fast, but ur not getting what u paid for tbh.

If u want those REAL speeds for video work, here's what i suggest:

1. Go for the SanDisk Professional PRO-G40 SSD 2TB. I use this one and it's basically a tank. It has a dual-mode controller so it hits full Thunderbolt 3/4 speeds (like 2700MB/s+) on ur iMac but also works on older USB-C gear. It runs cooler than most cuz the aluminum core acts like a heatsink.
2. Another solid option is the OWC Envoy Pro FX 2TB Portable NVMe SSD. These guys specialize in Mac stuff so the compatibility with Sequoia is basically guaranteed. It's super rugged and I've never seen mine throttle during long exports.
3. If ur trying to stay under $300, definitely check out the Crucial X10 Pro 2TB Portable SSD. It's tiny and cheap, but again, remember it might hit a speed ceiling on Mac compared to a true Thunderbolt drive.

Honestly, if ur doing heavy 4K editing, I'd suck it up and get the G40. It's better to spend a bit more now than deal with dropped frames later cuz ur drive got too hot and throttled. Just make sure to use the cable it comes with!! gl!

Seconded!

Just saw this thread and honestly, the technical side of this is a bit of a minefield. Before I can really weigh in, I gotta ask: what specific bitrates are you working with for your 4K footage? Are we talking high-bitrate ProRes or just standard compressed files? It makes a massive difference for sustained write performance versus burst speeds. I learned this the hard way with my current setup. I used to rely on a popular consumer-grade drive from one of the big brands, but it would always start fast and then crawl once the cache filled up during long exports. Basically, the thermal management was just non-existent. I eventually gave up on those pre-built retail drives and went the DIY route with a dedicated Thunderbolt enclosure and a high-end NVMe blade. The difference in how macOS handles the handshake over a true Thunderbolt controller compared to the cheaper bridge chips in many of those off-the-shelf drives is night and day. Some brands prioritize slim designs over heat dissipation, which is a total killer for video work... have you noticed if your current projects usually hit the drive hard for long periods, or is it mostly just moving smaller photo libraries?

> Since the M4 supports Thunderbolt 4, I want to make sure I’m getting something that actually hits those high transfer speeds without overheating.

Just sharing my experience: I went through this exact same struggle when I upgraded. I basically obsessed over read/write speeds because I didn't wanna waste money on a drive that would throttle while I was editing 4K footage in the middle of a project... tbh it’s a bit of a rabbit hole lol.

Before you pull the trigger, are you planning on running your actual apps off the drive, or is it strictly for file storage? Also, how long are your typical editing sessions?