Q: Cramfs Vs. Ubifs

[Ran Shalit]

Hello,

I read about cramfs and ubifs, but there is still something I don't
understand here, I hope you can help me with that...
1. It seems reasonable that execution from RAM is faster then Nand flash.
    So If I'm using ubifs, should I copy the executables to RAM before execute ?
2. If there is no need for writable filesystem, cramfs seems a good
choice, but some of the utilities write stuff to /var. How should we
handle that with cramfs ?
3. in terms of boot time, both cramfs and ubifs are equal. is it correct ?

Thank you,

Ran