Comment by exikyut

I've heard of those, they sound mildly interesting to play with, if just to go "huh" at and move on. I get the impression the main reason they developed a... strained reputation was their strong tendency to want to do RAID things (involving custom metadata and other proprietaryness) even for single disks, making data recovery scenarios that much more complicated and stressful if it hadn't been turned off. That's my naive projection though, I (obviously) have no real-world experience with these cards, I just knew to steer far away from them (heh)

An inline widget (SATA on both sides) that just implements a write cache and state machine ("push this data to these blocks on next power on") seems so much simpler. You could even have one for each disk and connect to a straightforward RAID/SAS controller. (Hmm, and if you externalize the battery component, you could have one battery connect to several units...)

You are indeed right about the battery/capacitor situation ("you have to open the case?!"), I wouldn't be surprised if the battery level reporting in those RAID cards was far from ideal too lol

With all this being said, a UPS is by far the simplest solution, naturally, but also the most transiently expensive.