Physical block addresses?

Physical block addresses?

[Sivan Toledo]

Hi,

I am trying to figure out whether NILFS uses physical block addresses
as pointers in inodes and indirect blocks, but I could not figure this
out from the papers.

Does it? If so, I assume that when cleaning a segment and copying live
data to a new segment, each relocated block causes the propagation of
dirty blocks (because some other blocks point to the old segment, so
they need to be modified, and so on. Is that correct?

Thanks, Sivan Toledo

Re: Physical block addresses?

[Koji Sato]

Hi, Sivan.

> I am trying to figure out whether NILFS uses physical block addresses
> as pointers in inodes and indirect blocks, but I could not figure this
> out from the papers.
> 
> Does it? If so, I assume that when cleaning a segment and copying live
> data to a new segment, each relocated block causes the propagation of
> dirty blocks (because some other blocks point to the old segment, so
> they need to be modified, and so on. Is that correct?

NILFS version 2 uses virtual block numbers to point to blocks. The
virtual block numbers are translated into physical disk addresses when
they are referenced. This mechanism prevents cascading updates of the
file system when cleaning segments because only the
virtual-to-physical mappings are updated.

Thanks.

-- 
Koji Sato
Open Source Software Computing Project
NTT Cyber Space Laboratories
Nippon Telegraph and Telephone Corporation