SD card Wear Leveling

njepsen · Joined: 13 Aug 2007 Posts: 469

If you Google this, Mr google says that some SD mfs do wear leveling and some appear not to. I have been told that writing to the FAT is not wear level protected, and this makes me nervous because:
In a data logger, I write about 3000 bytes of data to a new file on an SD card every 15 minutes, then I connect to a server & download from the file. If the download is good, i erase the file. If not, I try again in 15 minutes.
This i believe results in 2 FAT writes every 15 minutes, or 70,000 per year.
It has occurred to me, that i could write one file for say a month, and simply append my data to it every 15 minutes. Then i would only have 1 FAT write each month.
The problem i for-see is once I find a block, download it, how do mark it as 'done' so I get to skip it next time. I could append a tag to it if it was successfully downloaded, but I would then need to troll through a months worth of data to find out which blocks to download. Not sure how fast that would be.
Thoughts anyone?