which file system for sd card?

Helge Hafting helge.hafting at hist.no
Mon Jan 26 13:35:37 CET 2009

Fernando Martins wrote:
> Anyway, I'm also inclined for FAT, mostly for the simplicity (thus "less 
> susceptibility to corruption") and universality of the fs. I'm just left 
> wondering about performance, in particular as a storage for maps.

Maps will be read-mostly, right? So ext2 and ext3 will have the same 
performance, the journal will only cost some performance when writing.

You can customize the ext2/3 filesystems. The block size can be 1k, 2k 
or 4k. Bigger blocks generally have the best performance, but if many 
tiles are smaller than 2k, then a 2k block size will let you fit more on 
the card.

It is years since I made a FAT filesystem, I got the impression that you 
cannot have small (4k) blocks on a too large device. If the blocks are 
much bigger than your average file size, then you wast lots of space per 

I use 4k blocks as most tiles are bigger than 2k, except for the many 
copies of "the completely blank tile". The many blank tiles can be fixed 
by a script that turns them all into symlinks into the same file - 
saving lots of space. (0k instead of 4k per blank tile). FAT does not 
offer links, so you must have one file for each blank tile.

Helge Hafting

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