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How is raid implemented at the *disk* level?

If disks have 512-byte physical sectors, and you have 10 disks using RAID 50 with a 1MB stripe-size how does that work at the disk level?



Correct me if I'm wrong, but conceptually, there would be 2 spans each consisting of a RAID-5 array of 5 disks, one mirrored to the other. Therefore, a "stripe" would consist of 4x256KB chunks of data, plus a single 256KB of parity data per stripes? or does a "stripe" include the parity?



What if you consider a 12-disk RAID 10 array? There would be 6 mirrored pairs of disks, with striping over those mirrors. So, for a 1MB stripe size, the stripe would be divided by 6, for 174,762.666 bytes per-disk, which works out to 341.333 physical sectors per stripe. Is that really 342 physical sectors per stripe?



For those who wonder why I'm asking; I am attempting to determine the most efficient number of disks relative to the type of RAID, with the best stripe size.






Also, I have seen https://en.wikipedia.org/wiki/Nested_RAID_levels prior to asking this question. In fact, I've done a ton of work looking for low-level design details on a vast multitude of SCSI / SAS / RAID / SAN vendor sites, and have not seen anything that talks about the actual on-disk format of stripes. Stripes are only talked about at a highly conceptual level, which is fine, but doesn't really answer the question.

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