I’m not familiar with Fast-RTPS, my point is just that VSZ can be deceptive because there are many things that add into that which don’t affect resident memory at all; If Fast-RTPS uses memory-mapped files or has large shared libraries, it could easily balloon far beyond the size of your physical memory without having any negative impact. If the actual RSS value is growing enough that processes are being killed, you might want to look in to using a memory profiling tool like Google perftools or valgrind massif on your program to see what’s allocating so much.
As far as SD cards go, how much wear it can handle depends largely on the card. There are industrial SD cards that supposedly can handle hundreds of TB of writes before they fail, so they would last for years even if you’re writing hundreds of GB per day.