Hello,
I'm currently trying to understand the "flow" of the I/O in Linux raid1
devices in regard to superblock updates and resynces on machine crashes.
I looked at the source (2.6 kernel) and made some guesses about the
working of the raid1 kernel module. The problem is that I'm not an
kernel expert so I try to point out the basic algotithms and it would be
great if some expert could give ma a yes/no answer :)
1) As soon as the first write is made, the superblock is updated and
mddev->in_sync is set to 0
2) There is a machanism (can you tell me which part of the kernel does
this ?) that looks if all write requests have been written to both disks
and if no write requests are queued anymore, the superblock is updated
with the information mddev->in_sync=1
The question is, whats the maximal time that data can be "out of sync"
on both mirrors making the mirror an NON-synchronous mirror ?
Is there a way to make the mirror a "real" synchronous mirror ?
Regards,
Robert Heinzmann
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