understanding block distribution in UFS2 filesystems

[Jamie Ostrowski]

    I thought I understood how block distribution in UFS2 filesystems work,
until I tried running dumpfs on one of my filesystems. The output really
confused me, and the man page doesn't get into detail in explaining the
output. Can anyone explain why I am seeing references to the same "free
blocks" in different cylinder groups?

    I thought that the block numbers were unique across the entire
filesystem, but from the output of dumpfs, I see references to free blocks
0-7 in almost every cylinder group.

    So are the blocks that are in each cylinder group numbered start over
with a new block 0 in each cylinder group?

In other words, which picture below is true, A, or B:


Cylinder group 0: Uses blocks 0-4000

Cylinder group 1: Uses blocks 4001-8000

Cylinder group 2: Uses blocks 8001-12000



OR  -- B:


Cylinder group 0: Uses blocks 0-4000

Cylinder group 1: Uses blocks 0-8000

Cylinder group 2: Uses blocks 0-7000



(IE in that sense blocks must be referenced not only by the block number but
by the cylinder group they are in)



   I sure hope so, otherwise I am completely lost on this dumpfs output.
Thanks to anyone who can help clear up some of this confusion.


    - Jamie