I have been testing a few different combinations and I can share some results.
I started with a
Transcend 256GB JetDrive that I used to use on my Mac with a
Trancend USB 3.0 Card reader. I had read on here that GPT was better than MBR. (Note that most SSD cards/ USB drives come formatted as MBR with FAT32).
Unfortunately, this combo only worked for a few minutes before I got the dreaded too slow error. GPT was the culprit.
I check this combo with a simple dd test using sequential large blocks and it ran 1.3MB/s. I converted it to MBR and reformatted FAT32. DD ran about 11MB/s writes and 78 MB/s read. It gave no errors for TeslaCam with 1 day of driving around, but ran too hot. Too hot for my liking and I did't like how it stuck out of the usb port, could be prone to accidental breakage.
Not being a big fan of transcend as they have ****ed me over on warranty before (sent me a microscope pic of the gold on the microSD card contacts being worn from insertion/removal from their own SD card reader and rejected warranty - WTF!)
I ordered both a
SanDisk UltraFit 128GB USB Drive and a
SanDisk High Endurance 128GB microSDXC. What I found in my tests first was that they both come as MBR.
UltraFit gave 116MB/s read and 56MB/s write (specs: operating range 0C/32F to 35C/95F and 5 year warranty)
HighEndurance gave 85MB/s read and 74 MB/s write (specs: operating range -13F/-12C to 85C/185ºF and 10,000 Hrs of recording durability, but only a 2 year warranty)
Both of these meet the 10 MB/s or minimum threshold for TeslaCam with v9, maybe higher with V10 since it records rear cam as well, so to be safe let's say 15MB/s as a minimum. Read speed really doesn't matter much. Both have been working well swapping them out a few days each.
Here is the double edge sword: I like the fit of the ultrafit USB drive, it sits flush in the usb port and is completely unnoticeable in the dark console. It runs luke warm at best. The high endurance one needs to go into a adapter and after a number of different small form factor and even larger USB adapters, they all seem to run hella hot (too hot to touch) while being used for TeslaCam. So while I am glad that the SD card can handle 185F, the adapters seem to be the weak link (many bad reviews on amazon where the plastic on the outside of the SD card melts while inside the adapter). So have settled on the SanDisk UltraFit for now with the hope that SanDisk honors the 5 yr warranty if/when it crashes, as they have done in the past with many of their other SD cards in Camera. Unlike cheapo cards, the SanDisk will go into a ReadOnly mode before crapping out and allow you to copy off your files, just not write new ones.
I use the SanDisk high endurance 32GB in all my other cars where I have after market dashcams, but in these I do not have a little red icon as in the Tesla telling me recording is working and they run very cold as they accept microSD cards directly.
I left Sentry mode on at the airport this weekend for 2-day and it worked like a champ. Even though it was empty when I left and came back to being parked besides an F150 platinum on one side and dodge RAM on the other. I was able to see and appreciate how both truck drivers took time not to let their doors ding my Tesla or luggage scratch the paint , which has happened in the past.
One other mention-able thing is that the first time you take the TeslaCam card out and put into a Windows 10 PC, it will say there is an error and windows can fix it. Not sure what Windows is doing, but if you accept the fix, it is messing with the card making it flaky with TeslaCam after the fact. It seems to work better if you tell Windows not to fix it, as you can still see the video, whcih seems to play better on VLC than Windows player.
So for formatting, I used diskpart to convert between MBR and GPT and Gparted on Linux to format Full (not quick) FAT32 as windows is now exFAT only. Yet to try the setup with GPT which will reduce speed but hopefully well over 15MB/s and see how it performs. For Windows I recommend using SDFormatter utility from the organization that governs SD Card formats over an 3rd party utility.