Fat32 and large amounts of small files / Wasted space
Founder, firstly I am surprised that people write replys that are rude, incorrect, irrelevant and often stupid. I understand your problem.
I have just produced offline google street maps for Singapore down to level 19. That is over 137,000 files. Loading them onto a 16gb SD card formatted to standard FAT 32 took up 11.2gb of space.
The problem is that a default FAT 32 format makes clusters of 32k each and each cluster can only have one file in it. The .png tile files are slightly less than 1k but each one uses 32k of space.
But FAT32 format can be made to use different cluster sizes : -FAT32 supports 512, 1024, 2048, 4096, 8192, 16K, 32K, 64K,128K, 256K. I formatted my SD disk with a cluster size of 4096, I could not use a smaller size as there is a maximum of 4177918 clusters allowed on one disk.
Copying the files over they now use 1.8gb of space. But the maps load too slowly on my Phone. It does work though. Because of the time it takes to copy the files over on my present (slow) laptop (9hrs) I will be delaying any further experimentation for a while, but I am going to reformat the disk with 8192 size clusters and see how that works, I want to get it down to about 4-6 gb as I hope to load several other map areas on the disk, possibly going up to 500,000 files - but I will have to check as there are also limitations on the number of files in directories etc.
Opening a DOS cmd window (Start / Run and type cmd in the small window) the command to use is FORMAT X: /FS:FAT32 /A:4096 where X: is the letter corresponding to your SD disk and the last 3/4 characters are the cluster size you want (512, 1024, 2048, 4096, 8192, 16K, 32K)
I hope this helps, I will post the results of further formatting trials in the not too far off future