On Wed, Oct 13, 2010 at 01:51:22PM -0400, Chris Knadle wrote: > > On Wed, October 13, 2010 7:52 am, Matthias Johnson wrote: > > Yeah sorry. I meant to say fdisk -l shows the raid as this disk doesn't > > contain a valid partition table. Thinking about it more I think I > > understand. I guess that since software raid works by creating a virtual > > device and existing in /dev fdisk attempts to read this along with the > > individual disks but the md disks it does not understand. Seems pretty > > obvious now. > > > > Matthias Johnson > > You might be correct, but it doesn't sound right. Last I recall making a > mirrored disk using md raid, I had md mirroring filesystems that were on > /partitions/ on both disks. So as far as I recall, md works with > partitions. The instructions I just looked up for mdadm and Linux > software raid showed using md with partitions. It's apparently possible > to set up raid using the raw disk device, though -- but doing so seems to > be not recommended.
Yes, you can set it up (like anything in linux) on a partition or on a raw disk. Linux doesn't care what sort of block device it is. I, too, always preferred partition. Setting it up on a partition lets you a) flag the partition as being part of a raid and b) I believe it helps the kernel autoraid detection. Yes, pointing fdisk at a non-partition-table set of bytes at the front of a disk is going to get you VERY strange output. It'll also eat your raid data and kill the disk if you change anything in fdisk by mistake! -m
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