That seems to be mere happenstance. Using ext3 vs ext4 likely just slightly alters the exact IO pattern to cause a different number of md events. As long as the md event counter is not the same then adding the second modified disk back in causes a resync, destroying the changes specific to the second disk and going with the changes on the first detected disk.
That seems to be mere happenstance. Using ext3 vs ext4 likely just slightly alters the exact IO pattern to cause a different number of md events. As long as the md event counter is not the same then adding the second modified disk back in causes a resync, destroying the changes specific to the second disk and going with the changes on the first detected disk.