On Mon, Mar 8, 2010 at 12:58 PM, Robin Hill <robin@xxxxxxxxxxxxxxx> wrote: > On Mon Mar 08, 2010 at 12:39:26PM -0800, Mark Knecht wrote: > >> Hi all, >> I'm still very much on a steep learning curve about what I can do >> with Linux software RAID. In another thread this weekend a couple of >> responders discussed among themselves 3-disk RAID1 solutions that can >> survive if 2 disks die. I don't understand what that means. Can >> someone point me at a quick explanation? Is that really possible? >> >> In general I'm using a few Wikipedia pages and gravitate toward the >> diagrams as much as anything. >> >> http://en.wikipedia.org/wiki/RAID >> http://en.wikipedia.org/wiki/RAID1#RAID_1 >> >> RAID0 - striping, speed not reliability (2 disk minimum) >> RAID1 - duplicate data, no other protection (2 disk minimum) >> >> How do I build RAID1 using three drives? Just duplicate the data 3 >> times? If drives start going bad how do I determine which one or two >> are failing? (fsck? SMART?) With 3 drives 1 fail seems relatively >> straightforward to figure out, but 2? >> > A 3-disk RAID1 is just 3 duplicate copies, yes. And RAID only protects > against hardware failures, so you know which disk has failed because it > gets kicked out of the array as faulty. This is the same regardless of > how many mirrored copies you have (md will detect a write failure to a > drive and mark it as faulty - read errors will cause the failed block to > get rewritten). > > As for how to create it - it's just the same process as for a 2-disk > RAID1 but specifying 3 drives (assuming you're using Linux md software > RAID - if not, please specify what you're intending to use). The manual > page for mdadm should give you everything you need - do ask if there's > anything you want clarifying though. > > Cheers, > Robin Thanks Robin. Maybe I am getting smarter about this if I'm figuring out what others are talking about! ;-) Cheers, Mark -- 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
