[CentOS] Questions about software RAID, LVM.

[SilverTip257]

On Thu, Feb 14, 2013 at 11:58 PM, Ted Miller <tedlists at sbcglobal.net> wrote:

> On 02/04/2013 06:40 PM, Robert Heller wrote:
> > I am planning to increase the disk space on my desktop system.  It is
> > running CentOS 5.9 w/XEN.  I have two 160Gig 2.5" laptop (2.5") SATA
> drives
> > in two slots of a 4-slot hot swap bay configured like this:
> >
> > Disk /dev/sda: 160.0 GB, 160041885696 bytes
> > 255 heads, 63 sectors/track, 19457 cylinders
> > Units = cylinders of 16065 * 512 = 8225280 bytes
> >
> >     Device Boot      Start         End      Blocks   Id  System
> > /dev/sda1   *           1         125     1004031   fd  Linux raid
> autodetect
> > /dev/sda2             126       19457   155284290   fd  Linux raid
> autodetect
> >
> > Disk /dev/sdb: 160.0 GB, 160041885696 bytes
> > 255 heads, 63 sectors/track, 19457 cylinders
> > Units = cylinders of 16065 * 512 = 8225280 bytes
> >
> >     Device Boot      Start         End      Blocks   Id  System
> > /dev/sdb1   *           1         125     1004031   fd  Linux raid
> autodetect
> > /dev/sdb2             126       19457   155284290   fd  Linux raid
> autodetect
> >
> > sauron.deepsoft.com% cat /proc/mdstat
> > Personalities : [raid1]
> > md0 : active raid1 sdb1[1] sda1[0]
> >        1003904 blocks [2/2] [UU]
> >
> > md1 : active raid1 sdb2[1] sda2[0]
> >        155284224 blocks [2/2] [UU]
> >
> > unused devices:<none>
> >
> > That is I have two RAID1 arrays: a small (1Gig) one mounted as /boot
> > and a larger 148Gig one that is a LVM Volume Group (which contains a
> > pile of file systems, some for DOM0 and some that are for other VMs).
> > What I plan on doing is getting a pair of 320Gig 2.5" (laptop) SATA
> > disks and fail over the existing disks to this new pair.  I believe I
> > can then 'grow' the second RAID array to be like ~300Gig.  My question
> > is: what happens to the LVM Volume Group?  Will it grow when the RAID
> > array grows?
>
> Not on its own, but you can grow it.  I believe the recommended way to do
> the LVM volume is to
> partition new drive as type fd
>

LVM is 8e

Software RAID is fd


> install new PV on new partition (will be new, larger size)
> make new PV part of old volume group
> migrate all volumes on old PV onto new PV
> remove old PV from volume group
>
> You have to do this separately for each drive, but it isn't very hard.  Of
> course your boot partition will have to be handled separately.
>
>
This is what I said ;)
http://lists.centos.org/pipermail/centos/2013-February/131917.html


>
> > Or should I leave /dev/md1 its current size and create a
> > new RAID array and add this as a second PV and grow the Volume Group
> > that way?
>
> That is a solution to a different problem.  You would end up with a VG of
> about 450 GB total.  If that is what you want to do, that works too.
>
>
He has to leave /dev/md1 at its current size ... it's a raid1.


>  > The documentation is not clear as to what happens -- the VG
> > is marked 'resisable'.
> >
> > sauron.deepsoft.com% sudo pvdisplay
> >    --- Physical volume ---
> >    PV Name               /dev/md1
> >    VG Name               sauron
> >    PV Size               148.09 GB / not usable 768.00 KB
> >    Allocatable           yes
> >    PE Size (KByte)       4096
> >    Total PE              37911
> >    Free PE               204
> >    Allocated PE          37707
> >    PV UUID               ttB15B-3eWx-4ioj-TUvm-lAPM-z9rD-Prumee
> >
> > sauron.deepsoft.com% sudo vgdisplay
> >    --- Volume group ---
> >    VG Name               sauron
> >    System ID
> >    Format                lvm2
> >    Metadata Areas        1
> >    Metadata Sequence No  65
> >    VG Access             read/write
> >    VG Status             resizable
> >    MAX LV                0
> >    Cur LV                17
> >    Open LV               12
> >    Max PV                0
> >    Cur PV                1
> >    Act PV                1
> >    VG Size               148.09 GB
> >    PE Size               4.00 MB
> >    Total PE              37911
> >    Alloc PE / Size       37707 / 147.29 GB
> >    Free  PE / Size       204 / 816.00 MB
> >    VG UUID               qG8gCf-3vou-7dp2-Ar0B-p8jz-eXZF-3vOONr
> >
> Doesn't look like anyone answered your question, so I'll tell you that the
> answer is "Yes".
>
> Ted Miller
>
>
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-- 
---~~.~~---
Mike
//  SilverTip257  //