Posted Apr 4, 2008 19:34 UTC (Fri) by Cato (subscriber, #7643)
In reply to: UBIFS by NAR
Parent article: UBIFS
No. Basically there are two types of flash devices, in simple terms:
1. Consumer flash devices - SD Cards, USB sticks, etc - these emulate hard drives by use of a
Flash Translation Layer (FTL) that hides any bad eraseblocks (flash blocks) and does 'wear
levelling' i.e. ensuring that no single flash block is used too much. Flash blocks wear out
after 10K to 100K writes. Different consumer flash devices have different FTLs, and writing a
good FTL is apparently hard. Filesystems that work with such devices are all the normal Linux
hard drive ones - ext3, JFS, XFS, vfat - but they are wholly dependent on the FTL to work.
2. 'Raw' flash devices, aka Memory Technology Devices (MTDs). These are key parts of consumer
flash devices, but aren't usable directly without an FTL, which is not included. They expose
the differences between NOR and NAND flash (which are quite large). MTDs require an
MTD-specific filesystem, e.g. YAFFS, JFFS2, LogFS, etc, and some of these FSs are specific to
NAND or NOR technology.
I've just been reading up on this so some of the above may be slightly off - it's a
complicated area. The FAQs at http://www.linux-mtd.infradead.org/faq/general.html were quite
helpful, as were the LWN articles of course.