but we do need to maximize lifetime and reduce failure
Are you using industrial grade SD-cards?
Those high quality cards can really make a difference. We performed some tests in our company because we had problems with SD-card failures in one of our products. Using industrial cards, the reliability improved by factor >10.
Industrial cards are generally based on Single Level Cell (SLC) NAND flash memory which is much more reliable than MLC or TLC. They also have wider operating temperature ranges and are guaranteed to use the same components for each card (same flash, same controller, same everything). Cheap cards, even if labeled exactly the same can be technically totally different, making it impossible to provide consistent reliability.
Other (claimed) features are advanced wear-leveling algorithms, static data refresh, extensive burn in testing (to detect early fallout occasionally seen in any semiconductor technology) and so on.
As an example: ATP Industrial Grade microSD Card Specification
Are there tools, perhaps for specific manufacturers, that help me understand why the card is failing? Whether it's a memory problem, a controller problem, electrical problem, etc?
I know that some companies like ATP for example provide tools to monitor some sd-card properties. They mention
- Available Life Monitor Tool to check the remaining life of microSD card
- Supports S.M.A.R.T. (Self-Monitoring, Analysis and Reporting Technology) with SMART tool for Windows 2000/XP/Vista/7 and Linux
But i have no experience with those.
One main cause for SD-card failures is power failure. Data corruption and even some kind of lower-level corruption can occur. Even if the SD-card host is idle, the SD-card controller may perform internal operations like wear leveling. This was confirmed as we send some defective cards back to the manufacturer for inspection. They sometimes even had to re-initialize the card (something like telling the controller to re-scan and re-evaluate the whole flash) because of some unrecoverable errors.
(I am in no way affiliated with ATP, I was just recently checking them out in comparison to other industrial SD-card manufacturers like Pretec).