Bruce M Simpson <[EMAIL PROTECTED]> writes: > The feedback I've seen in FreeBSD forums regarding ATA write caching > tends to back up your original assertion.
It wouldn't be the first case of uninformed people reinforcing eachother's belief in incorrect information. > I wonder if vendor neutral, reproducible, scientific research has been > conducted into this issue. Scientific research? Since when does reverse engineering qualify as scientific research? > * NAND Flash embedded ATA controllers should not erase sectors > containing data unless absolutely necessary, to implement wear > levelling. No. Blocks which go from used to unused should be immediately erased. Otherwise, the device fills up with unused, unerased blocks and you end up having to erase a block every time you write to the device. Remember that cells in NAND flash can only be changed in one direction (one to zero for single-level flash) without being erased. As a result, there are very few cases (allocation bitmaps being one of them) where you can write to the same block of NAND flash multiple times without erasing it in between. > [I came across an alternative to JFFS2 awhile back whose name escapes > me, which might work for the SDIO arm stuff imp was playing with.] Specialized file systems such as JFFS and YAFFS are not very useful for flash media with built-in wear levelling, such as USB sticks or CF / SD cards. They are mostly useful for embedded devices with on-board NAND flash. DES -- Dag-Erling Smørgrav - [EMAIL PROTECTED] _______________________________________________ cvs-all@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/cvs-all To unsubscribe, send any mail to "[EMAIL PROTECTED]"
