From mboxrd@z Thu Jan 1 00:00:00 1970 From: Justin Piszcz Subject: Re: Removing devices from RAID-5 Date: Thu, 14 Jun 2007 15:15:43 -0400 (EDT) Message-ID: References: Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Return-path: In-Reply-To: Sender: linux-raid-owner@vger.kernel.org To: Rich Walker Cc: linux-raid@vger.kernel.org List-Id: linux-raid.ids On Thu, 14 Jun 2007, Rich Walker wrote: > Justin Piszcz writes: > >> On Thu, 14 Jun 2007, Rich Walker wrote: > > [snip] >>> >>> 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 > technical director 251 Liverpool Road | > need a Hand? London N1 1LX | +UK 20 7700 2487 > www.shadowrobot.com/hand/overview.shtml > > - > 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 > 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.