David Brown put forth on 2/23/2011 7:56 AM: > However, as disks get bigger, the chance of errors on any given disk is > increasing. And the fact remains that if you have a failure on a RAID10 > system, you then have a single point of failure during the rebuild > period - while with RAID6 you still have redundancy (obviously RAID5 is > far worse here). The problem isn't a 2nd whole drive failure during the rebuild, but a URE during rebuild: http://www.zdnet.com/blog/storage/why-raid-5-stops-working-in-2009/162 > I don't know if you've followed the recent "md road-map: 2011" thread (I > can't see any replies from you in the thread), but that is my reference > point here. Actually I haven't. Is Neil's motivation with this RAID5/6 "mirror rebuild" to avoid the URE problem? > Incidentally, what's your opinion on a RAID1+5 or RAID1+6 setup, where > you have a RAID5 or RAID6 build from RAID1 pairs? You get all the > rebuild benefits of RAID1 or RAID10, such as simple and fast direct > copies for rebuilds, and little performance degradation. But you also > get multiple failure redundancy from the RAID5 or RAID6. It could be > that it is excessive - that the extra redundancy is not worth the > performance cost (you still have poor small write performance). I don't care for and don't use parity RAID levels. Simple mirroring and RAID10 have served me well for a very long time. They have many advantages over parity RAID and few, if any, disadvantages. I've mentioned all of these in previous posts. -- Stan -- Stan -- 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
