On Mon, 2006-10-02 at 13:10 -0700, Scott Silva wrote: > >> I format hot add sda1 2 3 > >> cat /proc/mdstat it's all there > > > > Unless you created it with 3 members, the 3rd is added as a spare. > > Maybe I am too far down the message tree to get this, but I don't see how > taking one drive from a raid 5 array off site does any good. One drive on a > mirror gives you a backup. One drive in a raid5 just gives you a used hard > drive with not much possibility to recover anything. > But feel free to slap some sense into me if I am too far off. > I could see if you had a raid 5 array, and then mirrored that to a raid 1 > with the usb drive opposite the "entire" raid5 array you would have a viable > backup. But you could just as easily mount the drive and rsync to it to get > the same effect. It probably wasn't clear from that conversation but it was about RAID1. The number of mirrors isn't limited to 2, so you can create a 3 drive array with one missing. This gives you 2 full-time mirrors plus the ability to add an external drive periodically, let the sync complete, then remove and rotate it offsite. It is best to unmount it before the fail/remove step, but it can run during the sync and you don't have to shut down. -- Les Mikesell lesmikesell at gmail.com