Re: zeroing old superblocks & upgrading...

On Friday July 7, john@stoffel.org wrote:

Neil> But if you wanted to (and were running a fairly recent kernel) you
Neil> could
Neil>   mdadm --grow --bitmap=internal /dev/md0

Did this.  And now I can do mdadm -X /dev/hde1 to examine the bitmap,
but I think this totally blows.  To create a bitmap, I add it to an
md# device, but to examine it, I have to know which sub-devices to
query?  That's really not what I would expect.

Hmm... I can see that.
-X is a counterpart to -E
They are both letters from EXamine.  They both look at a component and
tell you want is there.
-D (--detail) reports on the array.  Maybe it should be give more
details about any bitmap....

Neil>   mdadm --grow --bitmap=none /dev/md0

Neil> and it should work with minimal resync...

So why would I want to remove the bitmap?

To return you to the state you started in.  You didn't have a bitmap
to start with, so I gave you a recipe that left you with no bitmap.  I
didn't want to assume anything about whether you want a bitmap or not.

Ofcouse, if you want to leave the bitmap there, that is fine.
Possibly even a good idea.

NeilBrown