quoted

quoted

I would think that
mdadm --grow --raid-devices=4 -z max /dev/md1 /dev/hdg2 /dev/hde2
/dev/sda2 /dev/hdk2

Make sure the new device is added as a spare first the -z should not be 
needed, by default it should use all space on the new drive.

On Thu, 14 Jun 2007, Justin Piszcz wrote:

On Thu, 14 Jun 2007, Rich Walker wrote:

quoted

Justin Piszcz [off-list ref] writes:

quoted

On Thu, 14 Jun 2007, Rich Walker wrote:

[snip]

quoted

quoted

The array is used as a single PV/VG for LVM.

What I want to do is to
(a) reduce the PV/VG so it would fit in 160*3 rather than 160*4
(b) remove the last 160GB drive, (hdi), taking the array from 4+1 to 4+0
(c) rearrange the array from 4+0 to 3+1
(d) grow the array to 250*3
(e) enlarge the PV/VG again.

I would think that
mdadm --grow --raid-devices=4 -z max /dev/md1 /dev/hdg2 /dev/hde2 
/dev/sda2 /dev/hdk2
would do steps (b),(c),(d) in one go - is this correct?

The linux kernel version running is 2.6.21.3 SMP.

As far as I know you cannot shrink any md raid in Linux.

Justin.

Step (c) shrinks the array, which would be a problem.

But the mdadm command given *should* actually grow the array (from 640GB
to 750GB) whilst reducing the number of disks...

Is this likely to work?

mdadm says:

thoth:/--# mdadm --grow --help
Usage: mdadm --grow device options

This usage causes mdadm to attempt to reconfigure a running array.
This is only possibly if the kernel being used supports a particular
reconfiguration.  This version only supports changing the number of
devices in a RAID1, and changing the active size of all devices in
a RAID1/4/5/6.

Options that are valid with the grow (-G --grow) mode are:
 --size=        -z   : Change the active size of devices in an array.
                     : This is useful if all devices have been replaced
                     : with larger devices.
 --raid-disks=  -n   : Change the number of active devices in a RAID1
                     : array.
thoth:/--# mdadm -V
mdadm - v2.5.6 - 9 November 2006
thoth:/--#

which makes me think it wouldn't...

cheers, Rich.

-- 
rich walker         |  Shadow Robot Company | rw@shadow.org.uk
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You can try it, otherwise grab the latest version of mdadm and go ahead and 
grow it.  I have grown a 1.8TB array to 3.3TB and it was a pretty old version 
of mdadm.

Justin.
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