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Forum Discussion
Disk spin-down problem, RN104, fw 6.2.0
Hello, I'm using RN104, 2 x 4GB WD RED in JBOD/Flex mode (I need no raid). No apps installed, samba, dlna services stopped to debug this issue. Http/https/ssh - enabled. I've enabled disk spin down...
Anything your approach could fix is also fixed by a normal scrub. Per mdgm's comment, bitrot protection goes beyond what md raid can fix.
The weakness in all RAID is that it recovers from missing (unreadable) blocks, but has no way to recover from wrong blocks that are readable. It can only provide erasure correction, not error correction.
Blending in the checksum allows you to identify blocks that might be bad, and then pretend they were erased, so they can be rebuilt. I've seen that approach used in other contexts, it is also a well understood technique if you are into this kind of stuff.
The main difference between our approaches is that I was simulating a read error/erasure, and you were assuming there must be one already happening. It's a small change, but it enables repairs that otherwise can't be made. For instance, if you attempt to fix an array failure by cloning bad disks to a good ones - in that case there are scattered blocks that are wrong, but readable. My approach can fix most of those errors, yours cannot.
But again, Netgear isn't saying what they actually did - probably because they want to retain it as a competitive advantage.
The weakness in all RAID is that it recovers from missing (unreadable) blocks, but has no way to recover from wrong blocks that are readable. It can only provide erasure correction, not error correction.
Blending in the checksum allows you to identify blocks that might be bad, and then pretend they were erased, so they can be rebuilt. I've seen that approach used in other contexts, it is also a well understood technique if you are into this kind of stuff.
The main difference between our approaches is that I was simulating a read error/erasure, and you were assuming there must be one already happening. It's a small change, but it enables repairs that otherwise can't be made. For instance, if you attempt to fix an array failure by cloning bad disks to a good ones - in that case there are scattered blocks that are wrong, but readable. My approach can fix most of those errors, yours cannot.
But again, Netgear isn't saying what they actually did - probably because they want to retain it as a competitive advantage.
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