On Mon, Mar 8, 2010 at 1:04 PM, Mark Knecht <markknecht@xxxxxxxxx> wrote: > 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 > When in doubt, read the manual two or three more times. This might also help you: http://wiki.tldp.org/LVM-on-RAID I wrote some background comparison sections when I made that... -- 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
