MIRRORLESS: GH7 + NVMe 2230 in CFexpress adapter: ProRes RAW 5.7K records long, then stops with “writing speed limitation” (odd remaining time)

Hi, I’m testing an NVMe-to-CFexpress setup with my Panasonic Lumix GH7 and I’m seeing confusing behavior and repeated “writing speed” errors.

My setup​

• Camera: Panasonic Lumix GH7
• Storage: Sabrent Rocket 2230 NVMe, 1TB
• Adapter: NVMe 2230 → CFexpress Type B adapter (from AliExpress)
• I have two adapters: one aluminum and one copper (copper should be better thermally, but the results below were with this general setup)
• In camera, I format the media and I also select “Low Level Format”

Test mode​

• Recording mode: ProRes RAW HQ 5.7K (this is mainly for testing; I don’t plan to use RAW heavily, but I want to understand the behavior)

What happens (step-by-step)​

1. With a freshly formatted NVMe (including Low Level Format), the GH7 shows:
   • Remaining time: 26 min 11 s
2. I press record. The camera actually records continuously for:
   • 37 min 39 s, then stops by itself
3. When it stops, the GH7 displays this message:
   • “Recording was cancelled due to the limitation of the writing speed of the card.”
     (So it did not stop because it ran out of space.)
4. Immediately after that long recording, the GH7 still shows:
   • Remaining time: 15 min 23 s
5. Then it gets worse:
   • I press REC again → it records ~17 s, then stops with the same “writing speed limitation” message
   • Try again → ~12 s, stops
   • Try again → ~11 s, stops
   • Even after waiting (cool down / idle), it still only records ~15 s and stops with the same message

File details​

I checked the recorded file on the media:

• File size: 601 GB
• Clip duration: 34 min 37 s

Questions​

1. Why would GH7 show 26:11 remaining, but then successfully record ~37 minutes (and later still show remaining time)?
2. Why does it record one long clip successfully (tens of minutes), but after that it can only record 10–20 seconds before failing with a write-speed limitation?
3. Is the “Remaining time” estimate unreliable for ProRes RAW, or does it suggest a bitrate/estimation mismatch?
4. Could this be related to:
   • NVMe SLC cache behavior / garbage collection
   • Thermal throttling (especially in a CFexpress-sized enclosure)
   • Adapter compatibility / controller behavior
   • Lack of proper TRIM/secure erase even with “Low Level Format” in-camera
5. Any recommended settings or supported media guidance for stable 5.7K ProRes RAW on GH7 (especially regarding CFexpress performance requirements)?

Any insights or recommended troubleshooting steps are appreciated. If Panasonic support can advise whether this behavior is expected when using NVMe-to-CFexpress adapters, that would also help.


Thanks!

The changing remaining time is common for all cameras because as you surmised they record with a variable bitrate so it can only be an estimate.

As for the rest always use what the manufacture recommends, no third party batteries, or anything that's not supported (memory cards or external drives). Cheap or knock off cards can advertise false speeds, some brands of cards aren't compatible with picky cameras.

Peter is correct about sticking with cards recommended by the manufacturer. I have been tempted to save a little money by buying a cheap interposer that adapts a cheaper-per-GB SSD to a camera card interface, but discovered that the advertised speed of an SSD isn't always sustained for the entire drive write. Googling the SSD you're using, I found an article that shows it doesn't use DRAM for caching, instead the controller writes to the NAND chip in a pseudo-SLC mode for some of its capacity and then drops down to a slower (but more silicon space efficient) TLC mode for the remaining capacity. A real CFexpress card would spec NAND with a higher write speed, or it might even use the same flash memory inside it, but go about writing to it differently. That is why you sometimes see odd sizes like 660GB; there are enough chips inside those cards for a larger raw capacity of ~2TB, but they're writing to it in a way that prioritizes speed.

FWIW, you can use external storage plugged into the GH7 (and the GH6 and G9m2) and record at the highest possible quality with the camera. I have a YouTube video demonstrating this with a Lexar 1TB SSD and my GH6: