Remember FAT32 is limited to files no larger than 4 GB so you will need eight or more files to fill a 32 GB card.
Recent versions of SdFat also supports SDXC cards when formatted FAT32 with the SdFat/examples/SdFormatter sketch. FAT32 is not the standard format for SDXC cards but PCs, Macs, and Linux accept FAT32 formatted cards.
I have tested with 64 and 128 GB SDXC cards.
How about 678 folders in root, each folder containing upto but no more than 400 files each.....approximately 29GB and 271,200 files..... all files same size 115200 bytes...
My current setup is 8GB SDHC with 144 folders in root, each folder contains exactly 400 files of 115200bytes.
128GB SDXC would be awesome, and negate my previous question of dis-mounting a card, and mounting another one on a live system...
Am I correct in thinking random access of directory entry 1000 is slower than directory entry 500, due to sequential access? Sorry for the newb type questions if this is supposed to be obvious. I have a general understanding of FAT32, but not the Arduino implementation. The reason I ask, when I access some of the previously mentioned files, access times can vary by upto 40ms I have seen, but repeated access of the same file, will yield the same access time, so is this slower access because it reads all entries until it locates the one requested?