how to move a raid1 drive to a new machine

how to move a raid1 drive to a new machine

[Mitchell Laks]

Hi gurus,

A simple question. I have studied the documents

Software raid howto
http://www.tldp.org/HOWTO/Boot+Root+Raid+LILO.html
and scoured google.

Given a raid1 on a machine 

/dev/md0 consists of /dev/hdc and /dev/hde.

I want to grab one of those disks and move it to a new machine and make it 
available there.

What I have thought about:

turn off machine. grab /dev/hde. put in new machine say at position
/dev/hdc (for grins).

now take an identical copy of /etc/raidtab from the original machine.
install it as /etc/raidtab
modprobe raid1
mknod /dev/md0 b 9 0 (if necessary).
raidstart /dev/md0

will this work? 

questions:
1) when do i do mkraid /dev/md0 (ie what does that do... will it zap all the 
stuff in /dev/hdc => ie what was on old /dev/hde??)
2) what is the mysterious failed-disk parameter in /etc/raidtab used for - ie 
will it help here preserve the data while we start up the raid.
3) lets say i want to start the raid without a partner drive, ie just with 
/dev/hdc ( "drive that used to be known as /dev/hde" "my apologies to glyph 
who used to be Prince"), what do i do???

Thanks,
Mitchell

 
 

Re: how to move a raid1 drive to a new machine

[wimpunk]

Hi,

Mitchell Laks wrote:
> Hi gurus,
> 
> A simple question. I have studied the documents
> 
> Software raid howto
> http://www.tldp.org/HOWTO/Boot+Root+Raid+LILO.html
> and scoured google.
> 
> Given a raid1 on a machine 
> 
> /dev/md0 consists of /dev/hdc and /dev/hde.
> 
> I want to grab one of those disks and move it to a new machine and make it 
> available there.

My experience: just put those drives in your new machine and it will 
run.  Btw, I didn't use any /etc/raidtab configuration, it worked out of 
the box.

> 
> What I have thought about:
> 
> turn off machine. grab /dev/hde. put in new machine say at position
> /dev/hdc (for grins).
> 
> now take an identical copy of /etc/raidtab from the original machine.
> install it as /etc/raidtab
> modprobe raid1
> mknod /dev/md0 b 9 0 (if necessary).
> raidstart /dev/md0
> 
> will this work? 

My partitions were autodetect (fd) and after loading the raid-modules it 
  worked fine...

> 
> questions:
> 1) when do i do mkraid /dev/md0 (ie what does that do... will it zap all the 
> stuff in /dev/hdc => ie what was on old /dev/hde??)

yep.

> 2) what is the mysterious failed-disk parameter in /etc/raidtab used for - ie 
> will it help here preserve the data while we start up the raid.

It's handy when you're moving from a normal disk to a raid-construction.

> 3) lets say i want to start the raid without a partner drive, ie just with 
> /dev/hdc ( "drive that used to be known as /dev/hde" "my apologies to glyph 
> who used to be Prince"), what do i do???

It starts with a failed disk.

> 
> Thanks,
> Mitchell
> 
>  
>  
> -
> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html