I'm about to set up a gentoo partition on a very low throughput device (sd card) for a raspberry pi. Are there any filesystems optimized to run as a root partition with low throughput and storage space?
There is a quite new filesystem called f2fs optimized for high level access to NAND flash memory, such as SD cards. The outstanding feature of f2fs is reduced wearing, which is the big issue with flash memory. The wearing is especially bad with journaling filesystems, and filesystems mounted with atime enabled. The throughput and storage capacity are not at all bad, compared to floppy disks for example. Any common filesystem like ext2 deals very well with this.