RAID Question

[Vu Pham]

> -----Original Message-----
> From: linux-users-bounces at linux-sxs.org 
> [mailto:linux-users-bounces at linux-sxs.org] On Behalf Of Alma J Wetzker
> Sent: Thursday, August 19, 2004 9:18 AM
> To: Linux tips and tricks
> Subject: RAID Question
> 
> I need to setup a system with hardware raid on the SATA 
> channels.  I have the two SATA drives set up as mirrors.  I 
> see three devices that I can identify:
> 
> /dev/hdd	cdrom
> /dev/hde	drive 0?
> /dev/hdg	drive 1?
> 
> I am expecting the RAID mirrors to be a separate device.  Is 
> that wrong?  I setup /dev/hdg and expect to see the 
> partitions reflected on /dev/hde, they are not.  The BIOS 
> still reports a mirror.  Am I doing this wrong?  What should 
> I be looking for?  Do I need to setup software RAID to copy 
> the hardware RAID?  There are no /dev/s* or other /dev/h* 
> devices that look like drives.
> 
> I am used to the RAID controller presenting me a single 
> device for the entire array.  I can get all the hardware 
> specifics this afternoon.  I was setting up several boxen and 
> can't find my notes.
> 

If you are using software RAID, then the partitions used for raid do not
have to be on separate physical devices. They can be all on the same hard
drive. Of course this soft RAID with partitions on same device gives almost
no data protection at all. In this case, the RAID device names are md0, md1
...

If you are using hardware RAID, then they must be on separate physical
devices, AFAIK. The device names in this case are sd0, sd1 ... for SCSI, as
if you have a single scsi device.

Vu