Re: Improving RAIDframe Parity Handling: The Diff

[Alan Barrett <apb%cequrux.com@localhost>]

On Sun, 01 Nov 2009, Jed Davis wrote:
> The RAID component label has a certain number of unused fields, which
> are zeroed on label creation and left unchanged otherwise.  Thus,
> allocating a bit from one of them to indicate that a parity-map kernel
> has ever touched the RAID suffices.  For determining what the last
> kernel to touch the RAID was, I'm storing a copy of the label
> modification counter (incremented whenever the label is changed to avoid
> combining inconsistent components) in another of the formerly unused
> fields; a non-parity-map kernel will leave the old number in place while
> incrementing the modification counter itself, so they will not match.

It seem to me that the extra counter would be sufficient, and that you
don't also need the extra status bit.  Essentially, you get the same
information from (extra copy of modification counter != 0) as you get
from the status bit.

--apb (Alan Barrett)