this topic contains highly interesting information. One thing was missing : real testing. Since the Sandisk High Endurance card was mentioned, I decided to buy one and test.
The test consists in writing series of :
10000 files of 17 bytes
1000 files of 17 KB
100 files of 17 MB
10 files of 170 MB
The total is around 3.5GB and is equivalent to writing 1MB every day for 10 years.
Then everything was read again and compared.
The card had only 8GB of free space (to evaluate the pseudo-leveling on free space, explained somewhere above.
First SD card tested had errors from the beginning, despite being from a known brand. Perhaps one day I will try again, but presently the test was discontinued.
Then I tested with the card arrived with the RPI with the Noobs distri. It ran without errors for 5000 cycles, which is the equivalent of writing 5GB of data every day for 10 years.
Then the errors appeared, and after 100 more cycles, the card died.
The conclusion of this test is that the wear leveling system is not bad. It does not use only the free space (the card would have died at 3000 cycles at most), but the general result is :
- 17.5 TB written,
- equivalent of 1093 writes on the full card.
- equivalent of writing 5GB every day for 10 years
Simultaneously, I was testing on a second Raspeberry Pi a Sandisk 32GB High Endurance card (the white card). The test lasted for 6 months, and then it was enough and I stopped it, to be able to use the card again. Result is :
- 70TB written
- 222 000 000 files
- equivalent of 2187 writes of the full card
- equivalent of writing 10GB in 30 000 files, every day for 20 years.
I could continue the test to the maximum possible of 28000 cycles (Erase count 3000), we cannot expect more. But presently i thought that the test was even better than expected, and I prefer to continue running my Raspberry Pi normally on this card.