[CentOS] A question about RAID and partitions

Miguel Medalha wrote:

> Yet, maybe I am being stupid but it seems to me that there still is 
> something to my original question...
> 
> Under hardware RAID, a dedicated processor on the RAID controller does 
> all the job of RAID calculations.
> Under software RAID, as you said, "you create partitions on the disk, 
> then combine them into md devices".
> 
> Isn't there any space for something in which the disks are made parts of 
> RAID arrays *before* the partitions are created and yet all the RAID 
> operations would be made by the main CPU and so it would still be 
> considered software RAID? What would happen if the equivalent of mdadm 
> was *included* in the OS kernel?

I'm not sure it would be possible to boot such a drive.  Hardware raid 
has the benefit of a bios that understands it at boot time.  Software 
raid1 only works for /boot because each of the mirrored partitions looks 
just like a normal one to bios and grub.   For non-boot drives you can 
get the same effect (and more) by putting the whole drive in one 
partition, combining those with raid, then running lvm on top of that.

-- 
   Les Mikesell
    lesmikesell at gmail.com