I try to keep two partitions in the sd memory. one of 1GB to use as /overlay. and the second one as /data. (optional: swap partition 512mb)
/dev/mmcblk0p0 /overlay
/dev/mmcblk0p1 /mnt/data
/dev/mmcblk0p2 /swap
try to use the overlay partition with the journal disabled, since it permanently created problems for me.
you can disable it at mkfs time with:
mkfs.ext4 -O ^has_journal
or after you run mkfs.ext4, you can disable the journal with:
tune2fs -O ^has_journal