Neil Brown schrieb:
On Tuesday May 15, mangoo@xxxxxxxx wrote:
Neil Brown schrieb:
(...)
An external bitmap means that if the link goes down, it keeps track of
which blocks are in sync and which aren't, and when the link comes
back up you re-add the missing device and the rebuild continues where
it left off.
mdadm --build /dev/md22 --level=1 --bitmap=/root/mybitmap \
--write-behind --raid-disks=2 /dev/localdevice --write-mostly /dev/remotedevice
One more question - is there a way to estimate the size of the bitmap
file? Does it depend on the size of the array?
What bitmap file size can I expect for a 600 GB array?
Due to internal implementation details, mdadm limits the size of the
bitmap to 2^20 bits. So the file will be 100K +/- 50%.
That will lead to about 1Meg per bit. If you have a failure, this
might mean you end up re-copying several megabytes more than you
really need to, but that should add up to less than one second.
Good, I was wondering if ~200 MB left I have on a filesystem would be
enough :)
--
Tomasz Chmielewski
http://wpkg.org
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