Sean McNeil wrote: > Neither of those filesystems are appropriate for sd cards. They have > wear leveling logic that is not necessary or a good thing as it is > already done in firmware for sd. An efficient journaled filesystem not > designed for memory devices (like ext3) would be best. > > A quick net reading tells me that wear leveling works by counting writes and remapping sectors. Still wearing doesn't go away. It's also not clear what are the limitations of wear leveling. How much space remapping requires (or is reserved beforehand) and thus how many sectors can be remapped and whether it also suffers from wearing problems itself.
Although wearing is not important for my specific use (mostly static storage of maps), I think a journaled file system essentially duplicates the writes in terms of data and might have some extra writes for extra data structures. Thus, speculating a bit, a journaled file system uses more space, causes more writings and can put more strain on wear leveling (the journal, in addition to the file system data structures). Another issue, actually the most important for this use, is read performance. FAT has the advantage of requiring simple logic but indexing it's poor (I think it does a sequential access on each relevant directory table). I guess it also depends a bit on the FAT implementation (I've read subjective claims that Linux implementation is not the best). Unfortunately a quick search didn't return really interesting benchmarks. Cheers, Fernando _______________________________________________ Openmoko community mailing list [email protected] http://lists.openmoko.org/mailman/listinfo/community
