RAID 0+1

Ted Mittelstaedt tedm at
Fri May 23 15:11:33 UTC 2008

> -----Original Message-----
> From: Nejc Škoberne [mailto:nejc at]
> Sent: Friday, May 23, 2008 2:06 AM
> To: Ted Mittelstaedt
> Cc: 'User Questions'
> Subject: Re: RAID 0+1
> Hey,
> > don't use gmirror and atacontrol at the same time.  Use one or
> the other.
> I don't. As I said:
>  > Then I would merge the second
>  > slice of all 4 drives into a 0+1 array (first gstriping and
>  > then gmirroring them). I somehow succeeded this, but I also
>  > get a WARNING when booting the system:
> So I am gstriping first and then gmirroring the stripes.
> And I am getting this warning message:
> >> WARNING: Expected rawoffset 0, found 63
> I don't know if I should worry about this or not.

You mentioned you used atacontrol to create the array, that's not
part of gmirror.

However in any case, you are not done.

What you need to do now is write some data to the array, then
unplug one of the sata connectors to the drive.  The array will
go into fault mode.  Then you need to add the disk back in
and see if the array will accept it, or if the array ends up scotching

A mirror is no good if it can't actually survive a fault.

I used to do this when selling servers to HP Proliants.  I'd have a
customer with me and go to one of our production, running HP servers,
eject a drive from the array, give it to the customer for inspection,
then plug it back in.  Other than the red light appearing on the
drive for a few minutes, the rebuild operation was entirely in
hardware, the server wouldn't even blink.

If your array can't do that, your just basically technically
masterbating with your system to feel good - it is in actuality
a completely worthless mirror setup.


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