-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 da...@lang.hm wrote: > On Wed, 4 Feb 2009, Mitch Bradley wrote: > >> http://wiki.laptop.org/go/How_to_Damage_a_FLASH_Storage_Device >> >> Read it and weep. > > this completely ignores wear leveling, which is very nessasary for just > about any filesystem, but especially for FAT (which appear to be the only > filesystems this author is familiar with)
Umm, what? "To alleviate the "wear out" problems, the FTL must move data around so that repeated writes to a given sector don't cause too many writes to the same NAND page." Mitch is describing "FLASH" devices like SD cards. All such devices have a built-in microcontroller (the FTL) that performs wear-leveling. Layering additional wear-leveling filesystems like JFFS2 or UBIFS on top of the FTL requires a reverse translation (block device->MTD) and is not recommended. e.g. From http://www.linux-mtd.infradead.org/doc/ubifs.html : "UBIFS was designed to work on top of raw flash, which has nothing to do with block devices. This is why UBIFS does not work on MMC cards and the like - they look like block devices to the outside world because they implement FTL (Flash Translation Layer) support in hardware, which simply speaking emulates a block device" As for the author only being familiar with FAT, that is hilarious. Mitch implemented JFFS2 support in OFW, and wrote this page to explain how he produced optimal ext2 formatting of FTL FLASH. Indeed, that is the subject of http://wiki.laptop.org/go/How_to_Damage_a_FLASH_Storage_Device#Screwed-Up_Formatting - --Ben -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.9 (GNU/Linux) iEYEARECAAYFAkmJq7wACgkQUJT6e6HFtqT4sACdH/YR07Eq+l+i2M53HuWlZbF3 6bYAn3Aw3X7+k+cThHg9elaI/Jjiokp/ =6lfi -----END PGP SIGNATURE----- _______________________________________________ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel