On 05/17/2012 07:04 AM, John Robinson wrote: > On 17/05/2012 14:18, David Brown wrote: > [...] >> Theoretically, a 3-disk RAID6 is like a 2-disk RAID5 or a 1-disk RAID1 - > [...] >> I can't think of any good reason for it /not/ to support 3-disk >> RAID6, as there is nothing in the algorithms to hinder it. > > I've a vague recollection of Peter Anvin saying the implementation is > optimised in such a way that it won't work. > Yes, it would have required introducing some odd special cases. A 3-disk RAID-6 is bitwise identical to a 3-disk RAID-1, so if Neil wants to he could add "instant reshaping" support in mdadm (add a disk to a 3-disk RAID-1 turning it into a 4-disk RAID-6; and similar for 2-disk RAID-1 into 3-disk RAID-5.) -hpa -- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf. -- 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
