Hi again David, > Yes, being a generator for GF(2^8) is a requirement for a parity > generator (sorry for the confusing terminology here - if anyone has > a better suggestion, please say) to be part of a 255 data disk > system. However, being a GF generator is necessary but not > sufficient - using parity generators (1, 2, 4, 16) will /not/ give > quad parity for 255 data disks, even though individually each of 1, > 2, 4 and 16 are generators for GF. I ask again, could you please elaborate this? I nowhere found such a further constrain for the parities. All I could find is that the Vandermonde matrix must be done with generators. > 255 data disks is the theoretical limit for GF(2⁸). But it is a > theoretical limit of the algorithms - I don't know whether Linux md > raid actually supports that many disks. I certainly doubt if it is > useful. The reason to use many disks is in case of geo-redundant RAID, for example with iscsi. In this situation you want to have a lot of redundance, in parities, not mirror. bye, -- piergiorgio -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
