Yes, you should be able to do it either way. I have built 6+ drive arrays from clean install before without any problem. IIRC, the command should just be mdadm /dev/md0 -level=5 -raid-devices=4 /dev/sd[a-d]1 You can also add a switch to force all drives active but you must also add -ff to the command line. On Jan 22, 2010 3:56 PM, "Carlos Williams" <carloswill@xxxxxxxxx> wrote: On Fri, Jan 22, 2010 at 2:34 PM, Robert Howard <rjh0507@xxxxxxx> wrote: > RAID5 is one of the levels... I don't doubt that I could build a working Arch system with 3 physical drives and then use 'mdadm' to add the 4th drive as a spare or as additional disk space for the RAID5 array. I should be able to add a 4th disk to RAID5 w/o having any 'hot spares, correct? I just feel that I should be able to do this from a fresh install. I assumed I was missing a syntax in the command. I partition all 4 disks identical. All disks have a equal amount of partition space assigned to RAID (type = fd) and then I use mdadm to build the array so I can't see why it does not work. Yes I do have a USB keyboard but if I don't need to add the usb modules for RAID5 with 3 disks, why would I need to add it for RAID5 with 4 disks. It makes no sense to me...
