Hi All.
Summary: what's the deal with chunks/sectors/blocks/stripes, and how do they relate?
Longtime md raid user here, but have a silly question about terminology & units reported by the md system. This is prompted by mismatches reported in my new raid6 array (Fedora 28):
[...] mismatch sector in range 2742887048-2742887056
[...]
So, I want to see where on my array & filesystem those errors are. Syslog messages from md tell me:
detected capacity change from 0 to 24003968237568
That must be bytes. mdadm tells me
Version : 1.2
Array Size : 23441375232
Chunk Size : 512K
That size must be in KB.
/proc/mdstat says my array size is:
23441375232 blocks
So I infer that block size is 1KB.
OK, now how do the sectors reported by the raid-check relate to blocks or chunks? Or do they refer to the physical or logical sectors of the drive device (or partition) itself?
Also, the raid6check utility wants me to specify ranges in stripes. How do I find out anything about the stripe size of my array? Does it relate to the chunk size? How do I go from sector range to a stripe range?
And is there a way to go from the sector range to a range of ext4 blocks?
Lastly, is the raid6check program (from mdadm-4.0) considered a safe/reliable way to repair mismatches on raid6 arrays?
Thanks in advance,
-Matt
PS: Incidentally, all 5 drives are new WD Red 8TB drives that pass all smart tests and report 0 pending or reallocated sectors.
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