I noticed that softraid's RAID 5 implementation uses the left asymmetric layout, while I've only found (sparse/vague) documentation suggesting symmetric layouts should be slightly better (namely, for an N-disk array, every N consecutive data units will each be stored on a different disk) without any apparent disadvantage. Is there an advantage to asymmetric layouts that I'm not aware of?
It seems like it would be a fairly non-intrusive change: simply changing lines 423--424 of softraid_raidp.c to "chunk = (parity + 1 + chunk) % (no_chunk + 1);", though I haven't tested this. Of course, RAID 5 users would have to recreate their RAID arrays, but upgrading from 4.7 to 4.8 will require that anyway.
