[X-Unix] Hardware RAID Setup

[Stroller]

On 12 May 2010, at 20:06, Martin McCormick wrote:

> Eric F Crist writes:
>> Funny question, have you formatted the new raid device?
>
> 	No and I bet that is the problem. Since one drive
> originally had the OS on it, I was hoping that the raid card
> would mirror that bootable disk to the other disk sort of like
> dd will do if you do something like
>
> dd if=/dev/dev0 if=/dev/dev1
>
> For all I know, it mirrored the blank disk to the bootable disk.:-(
>
> 	This is the first time I have ever set up a raid 1
> controller so there are great knowledge gaps in my head.

Like I say, never used RAID on Macs, but a little bit on Linux now  
(with at least 3 different controllers).

When you initialise the array it will wipe out any data on the disks.  
The long wait you mentioned was the drives zeroing out. After the  
initialisation is completed, the two drives of a RAID1 array will  
always (in normal use) contain identical copies of data (subject to  
the completion of writes on each).

The initialisation will (surely) NOT mirror existing data to an array  
during creation, although some RAID controllers / userspace utilities  
offer a "migrate" command.

What you could do, for instance, if you have a working installation of  
MacOS on drive A, is to build an array Z from drives B & C. Then dd  
from A to Z. I have undertaken some variations of this under Linux;  
depending upon the complexity of what you're undertaking it can be  
either very easy and straightforward or time-consuming and somewhat  
harrowing.

You will likely only be able to use the drives when connected to the  
controller - i.e. you cannot remove one drive and read it on a  
different computer, unless that machine has the same RAID controller.  
If one drive fails you will be prompted to replace the drive - you  
should be able to work with only the single drive in the meantime.  
After you replace the failed drive the array will be rebuilt (copied,  
effectively) onto the new disk, and again you should be able to use  
the system during this rebuild process (disk operations will be  
slowed, as your use of the disk is effectively "shared" with the  
rebuild).

Stroller.