sorry for bringing this topic up after quite some time, but i would like to ask one question regarding TomCollins answer...
As you mentioned:
"The hardware includes a 1MB SPI flash split in half, with one half used for OTA firmware updates and the other half used for the file system. There's some overhead there, so you end up with less than 512KB available for file storage."
What exactly is the overhead that are you referring to?
Thank you in advance and sorry for the inconvenience