Neil Brown wrote: > (*) The term 'mirror' for raid1 has always bothered me because a > mirror presents a reflected image, while raid1 copies the data without > any transformation. > > With a 2drive raid5, one drive gets the original data, and the other > drive gets the data after it has been 'reflected' through an XOR > operation, so maybe a 2drive raid5 is really a 'mirrored' pair.... > Except that the data is still the same as XOR with 0 produces no > change. > So, if we made a tiny change to raid5 and got the xor operation to > start with 0xff in every byte, then the XOR would "reflect" each byte > in a reasonable meaningful way, and we might actually get a "mirrored > pair"!!! > > But I don't think that would provide any real value :-) Why not? Consider disks w/ 100mb/s thruput (theoretical): 2disk raid0 stripes data to yield 200mb/s read/write thruput. 2disk raid5 stripes data to yield 100mb/s write, 200mb/s read thruput always. 2disk raid1 mirrors data to yield 100mb/s write, 100/200mb/s single/multiple read thruput only. Would you think that this is enough of a real value? Thanks! -- Al - 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
