Можно в 2х словах?
В новости написано что оптимизированно для флеш накопителей, а на офф странице проекта:
One thing people have to understand when dealing with UBIFS is that UBIFS is very different to any traditional file system - it does not work on top of block devices (like hard drive, an SD card, an USB stick, etc). It was designed to work on top of UBI volumes, which have nothing to do with block devices. This is why UBIFS does not work on MMC cards or USB flash sticks - 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 on top of the built-in flash chip.
А я уж было подорвался смотреть как slax или кого-то на подобе на неё повесить.
