[linux-lvm] Cleanly removing a PV from an LV or, how do I get more available extents?

[linux-lvm] Cleanly removing a PV from an LV or, how do I get more available extents?

[Bharat Mediratta]

I've been happily using LVM for a couple of months now to aggregate a 
bunch of disks together into one logical drive for a Debian box that I 
use as an over-the-network backup of my various other boxen.  Thus far, 
it's been great.

Recently however, I started getting parity errors on one of the drives 
that's in my logical volume.  It's a tiny drive that I threw in there 
merely because I had it, and its loss will not be missed.  I just want 
to remove it altogether and pretend like it never existed.  I'd like to 
preserve the data that's on the drive, if possible, but if not -- I'm ok 
  with losing it, since that data will come back next time I run my backups.

I read the FAQ, the HOWTO and scanned the mailing list archives and it 
appears that I need to do a pvmove to get the data off of that drive, 
and then a vgreduce to remove it from the volume group.  Unfortunately, 
when I try to do the pvmove, I get:

% pvmove /dev/sdb
No extents available for allocation

I'm assuming that this means that there's nowhere to move the data that 
is on /dev/sdb.  I further assume this means that I need some free 
physical extents somewhere.  This is where I'm confused.  When I set up 
LVM, I allocated all of my spare drives to it.  So I have a 271GB
logical volume of which I'm using only 32GB.  So I know that I have free 
space to move the data around; I just don't know how to do it.

So.  How do I get more free physical extents inside my logical volume? 
I feel confident that there's an easy answer for this that I overlooked, 
but I can't find it.  Hopefully the context below will help a bit.

Thanks in advance,
-Bharat

================================

% lvdisplay
   --- Logical volume ---
   LV Name                /dev/data/data1
   VG Name                data
   LV UUID                abrnMJ-2MqB-tkQl-g8g6-xYXx-KLE8-PMbNdG
   LV Write Access        read/write
   LV Status              available
   # open                 1
   LV Size                275.19 GB
   Current LE             70448
   Segments               4
   Allocation             inherit
   Read ahead sectors     0
   Block device           254:0

% vgdisplay
   --- Volume group ---
   VG Name               data
   System ID
   Format                lvm2
   Metadata Areas        4
   Metadata Sequence No  8
   VG Access             read/write
   VG Status             resizable
   MAX LV                255
   Cur LV                1
   Open LV               1
   Max PV                255
   Cur PV                4
   Act PV                4
   VG Size               275.19 GB
   PE Size               4.00 MB
   Total PE              70448
   Alloc PE / Size       70448 / 275.19 GB
   Free  PE / Size       0 / 0
   VG UUID               PjytLd-X99E-iUTf-drKH-42dl-2QHO-6qBcmB

% pvdisplay
   --- Physical volume ---
   PV Name               /dev/sda
   VG Name               data
   PV Size               34.20 GB / not usable 0
   Allocatable           yes (but full)
   PE Size (KByte)       4096
   Total PE              8755
   Free PE               0
   Allocated PE          8755
   PV UUID               q8ElTG-XOoB-nQy6-8VTU-wZlR-uj3b-Vrnxlp

   --- Physical volume ---
   PV Name               /dev/sdb
   VG Name               data
   PV Size               8.55 GB / not usable 0
   Allocatable           yes (but full)
   PE Size (KByte)       4096
   Total PE              2189
   Free PE               0
   Allocated PE          2189
   PV UUID               dDZOFg-nQES-cCgO-l5KF-9JIz-i2hh-OpcP1V

   --- Physical volume ---
   PV Name               /dev/sdc
   VG Name               data
   PV Size               34.25 GB / not usable 0
   Allocatable           yes (but full)
   PE Size (KByte)       4096
   Total PE              8768
   Free PE               0
   Allocated PE          8768
   PV UUID               B8dtE3-gdB7-aakQ-p4EY-CysX-b6VU-LrBYmc

   --- Physical volume ---
   PV Name               /dev/hde7
   VG Name               data
   PV Size               198.19 GB / not usable 0
   Allocatable           yes (but full)
   PE Size (KByte)       4096
   Total PE              50736
   Free PE               0
   Allocated PE          50736
   PV UUID               bz31lu-ck6I-439l-IbWs-hb40-g6rm-rWE3oq

Re: [linux-lvm] Cleanly removing a PV from an LV or, how do I get more available extents?

[Dax Kelson]

On Sat, 2004-07-17 at 15:49, Bharat Mediratta wrote:
> I've been happily using LVM for a couple of months now to aggregate a 
> bunch of disks together into one logical drive for a Debian box that I 
> use as an over-the-network backup of my various other boxen.  Thus far, 
> it's been great.
> 
> Recently however, I started getting parity errors on one of the drives 
> that's in my logical volume.  It's a tiny drive that I threw in there 
> merely because I had it, and its loss will not be missed.  I just want 
> to remove it altogether and pretend like it never existed.  I'd like to 
> preserve the data that's on the drive, if possible, but if not -- I'm ok 
>   with losing it, since that data will come back next time I run my backups.
> 
> I read the FAQ, the HOWTO and scanned the mailing list archives and it 
> appears that I need to do a pvmove to get the data off of that drive, 
> and then a vgreduce to remove it from the volume group.  Unfortunately, 
> when I try to do the pvmove, I get:
> 
> % pvmove /dev/sdb
> No extents available for allocation
> 
> I'm assuming that this means that there's nowhere to move the data that 
> is on /dev/sdb.  I further assume this means that I need some free 
> physical extents somewhere.  This is where I'm confused.  When I set up 
> LVM, I allocated all of my spare drives to it.  So I have a 271GB
> logical volume of which I'm using only 32GB.  So I know that I have free 
> space to move the data around; I just don't know how to do it.

Your logical volume is 100% used by the filesystem. It sounds like the
filesystem isn't full though, but LVM doesn't know that.

You need to shrink your filesystem, then shrink your LV, then use
pvmove.

Dax Kelson
Guru Labs