On Wed, Dec 3, 2008 at 2:01 AM, Frantisek Dufka <dufkaf@xxxxxxxxx> wrote: > Mark wrote: >> >> On Tue, Dec 2, 2008 at 9:36 AM, Igor Stoppa <igor.stoppa@xxxxxxxxx> wrote: >>> >>> I can only repeat my advice: why don't you do some reading at least >>> about jffs2? >>> >> >> Because it's irrelevant in discussions about removable flash memory. > > How do you know if you did not read it? :-) I wouldn't be surprised if jffs2 > technical documentation would discuss NAND pecularities and wear levelling > details. > Because I have read it, and lots of other stuff. > Also http://en.wikipedia.org/wiki/Wear_leveling and pdf whitepapers linked > on the bottom could explain a lot. > >> Another issue is that wear levelling depends on there being a certain >> amount of free memory in order to shuffle the data around. Most use >> dynamic rather than static wear levelling, which reduces the >> effectiveness even further when there is little free space. > > Flash translation layer in memory cards does not know about 'free space', > that is filesystem related thing one layer above, we are talking about pure > data blocks with no meaning here. > > That is actually one thing to improve in future, filesystem should let the > flash device driver know which blocks are free so it can be more creative > with them. > > Frantisek > ...by which you're admitting that no wear levelling algorithm is perfect... Let's go back to the original question: how reliable are flash memory cards when used for booting an OS? Answer: Probably "reliable enough", provided something else doesn't go wrong. Flash cards *do* sometimes fail, for varying reasons, and repeated writes aren't the only issue. Mark _______________________________________________ maemo-users mailing list maemo-users@xxxxxxxxx https://lists.maemo.org/mailman/listinfo/maemo-users
