On Thu, Feb 25, 2010 at 10:31 AM, John Robinson <john.robinson@xxxxxxxxxxxxxxxx> wrote: > On 25/02/2010 17:41, Dawning Sky wrote: >> >> On Thu, Feb 25, 2010 at 8:45 AM, John Robinson >> <john.robinson@xxxxxxxxxxxxxxxx> wrote: >>> >>> On 25/02/2010 08:05, Giovanni Tessore wrote: >>> [...] >>> I do think we urgently need the hot reconstruction/recovery feature, so >>> failing drives can be recovered to fresh drives with two sources of data, >>> i.e. both the failing drive and the remaining drives in the array, giving >>> us >>> two chances of recovering every sector. >> >> I was one of those 4 cases in the part month. I would have certainly >> benefited from this when I tried to replace a failing drive on my old >> raid-5. But I think actually the redundancy you desired can be >> achieved by running a raid-6 at the degraded mode (with 1 missing >> drive). >> >> Do I miss something? If this is the case, shouldn't we all >> be doing this instead of using the raid-5? > > I think you must be missing something, yes. RAID-6 with one drive missing > would have 2 chances of recovering each sector, but then so does RAID-5 with > no drives missing. In either case, lose a drive and you need every sector on > the remaining drives to be good to complete the reconstruction and keep the > array up. > > Cheers, > > John. > > -- > 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 > No, what they're saying is that often drives don't /totally/ fail. They have segments that go bad first, and we are often catching them in that state. To use the segments that /are/ successfully returned there is a good chance that multiple 'not full member' drive could provide a complete, or usefully very near complete with known 'dead' areas set to store on fresh devices. -- 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
