When creating a linux software raid device as a raid10 device, I am confused why it must be initialized. The same question applies for raid1 or raid0, really.
Ultimately most people would put a file system of some sort on top of it, and that filesystem should not assume any state of the disk's data. Each write will affect both disks in a raid10 or raid1 setup, where the N mirrors are written to. There should be no reason whatsoever for a raid10 to be initialized initially, as it will happen over time.
I can understand why for a raid5/6 setup where there is a parity requirement, but even then it seems like this could be done lazily.
Is it just so people feel better about it?
Best Answer
Initial synchronization is needed because any differences between the mirrors would show up as errors during the periodic check.
And you should be doing periodic checks.