Lines Matching +full:on +full:- +full:flash
1 .. SPDX-License-Identifier: GPL-2.0
10 UBIFS file-system stands for UBI File System. UBI stands for "Unsorted
11 Block Images". UBIFS is a flash file system, which means it is designed
12 to work with flash devices. It is important to understand, that UBIFS
13 is completely different to any traditional file-system in Linux, like
14 Ext2, XFS, JFS, etc. UBIFS represents a separate class of file-systems
16 file-system of this class is JFFS2.
21 1 MTD devices represent flash devices and they consist of eraseblocks of
24 2 MTD devices support 3 main operations - read from some offset within an
26 eraseblock. Block devices support 2 main operations - read a whole
29 re-write its contents. Blocks may be just re-written.
30 4 Eraseblocks become worn out after some number of erase cycles -
31 typically 100K-1G for SLC NAND and NOR flashes, and 1K-10K for MLC
32 NAND flashes. Blocks do not have the wear-out property.
33 5 Eraseblocks may become bad (only on NAND flashes) and software should
34 deal with this. Blocks on hard drives typically do not become bad,
39 file-systems.
41 UBIFS works on top of UBI. UBI is a separate software layer which may be
43 wear-leveling layer. It provides so called UBI volumes which is a higher
45 is very similar to MTD devices - they still consist of large eraseblocks,
49 In a sense, UBIFS is a next generation of JFFS2 file-system, but it is
53 * JFFS2 works on top of MTD devices, UBIFS depends on UBI and works on
55 * JFFS2 does not have on-media index and has to build it while mounting,
57 information on the flash media and does not require full media scan,
59 * JFFS2 is a write-through file-system, while UBIFS supports write-back,
60 which makes UBIFS much faster on writes.
62 Similarly to JFFS2, UBIFS supports on-the-fly compression which makes
63 it possible to fit quite a lot of data to the flash.
65 Similarly to JFFS2, UBIFS is tolerant of unclean reboots and power-cuts.
67 journal and recovers from crashes, ensuring that the on-flash data
72 on the flash size, like in case of JFFS2. This is because UBIFS
73 maintains the FS index on the flash media. However, UBIFS depends on
89 bulk_read read more in one go to take advantage of flash
91 no_bulk_read (*) do not bulk-read
92 no_chk_data_crc (*) skip checking of CRCs on data nodes in order to
94 if the flash media is highly reliable. The effect
97 chk_data_crc do not skip checking CRCs on data nodes
118 Mount volume 0 on UBI device 0 to /mnt/ubifs::
120 $ mount -t ubifs ubi0_0 /mnt/ubifs
125 $ mount -t ubifs ubi0:rootfs /mnt/ubifs
136 - http://www.linux-mtd.infradead.org/doc/ubifs.html
137 - http://www.linux-mtd.infradead.org/faq/ubifs.html