On 21/05/2020 23:52, David T-G wrote:
Roger, et al --
...and then Roger Heflin said...
%
% For re-add to work the array must have a bitmap, so that mdadm knows
% what parts of the disk need updating.
[snip]
Ahhhhh... Thanks!
I've wondered about an internal bitmap vs not. I also wonder how big the
bitmap is and where else I might stick it ...
Bear in mind the bitmap is obsolete ... I need to get my head round it,
but you should upgrade from bitmap to journal ... amongst other things,
this fixes the "raid 5 write hole" - not sure what it is but it seems
inherent in the design of raid 5 that if something goes wrong it is easy
to lose data. Journalling presumably fixes that the same way it fixes
write losses in general ...
(Oh - and if you somehow manage to switch on bitmaps and journals
together the resulting array will refuse to assemble. The current tools
won't let you have both, but older versions can.)
Cheers,
Wol
