shrink partition after LVM resize on RedHat Linux

Question

I have a physical Redhat RHEL 6.10 machine on physical hardware, which I tried to virtualize for vmware. We did backup with dd to virtualize. Problem is right now, that this VM is still taking full 146GB-SAS-Disk of dataspace (original), but real data takes only 27GB of diskspace.

I resized the logical volume of partition /dev/mapper/vg_sb00681-lv_root and /dev/mapper/vg_sb00681-lv_home with command resize2fs and lvreduce (like described here: https://www.linuxtechi.com/reduce-size-lvm-partition/) of root-Parition to 20GB and home-Partition to 5GB. As you can see, partitions are shrinked. Still no problem.

Filesystem                      Size    Used    Avail   Use%    Mounted on
/dev/mapper/vg_sb00681-lv_root  20G     9.8G    8.9G    53%     /
tmpfs                           931M    0       931M    0%      /dev/shm
/dev/sda1                       477M    105M    347M    24%     /boot
/dev/mapper/vg_sb00681-lv_home  4.8G    1.5G    3.2G    32%     home

Now, with GParted I'm not able to free the free space on LVM partition.

If I tried to shrink/move partition, it ends in GParted with error. Error Message:

shrink file system
    lvm pvresize -v --yes --setphysicalvolumesize 34433024K '/dev/sda2'
        0 physical volume(s) resized or updated / 1 physical volume(s) not resized
        
        Archiving volume group "vg_sb00681" metadata (seqno 32).
        WARNING: /dev/sda2: Pretending size is 68866048 not 285650944 sectors.
        Resizing volume "/dev/sda2" to 68866048 sectors.
        Resizing physical volume /dev/sda2 from 34869 to 8406 extents.
        /dev/sda2: cannot resize to 8406 extents as later ones are allocated.

So I tried with pvmove to move physical extents to the end of physical volume. It gaves me free disk space between the physical volumes and I'm not able to pack free space together to the end. I've no idea what the next steps are and if it is possible to reduce partition on VM to save disk space.

ubuntu@ubuntu:-$ sudo pvs -v --segments /dev/sda2
PV          VG          Fmt     Attr    PSize   PFree   Start       SSize   LV          Stat    Type    PE Ranges
/dev/sda2   vg_sb00681  lvm2    a--     <136.21g 103.37g    0       2006    lv_swap     0       linear  /dev/sda2:0-2005
/dev/sda2   vg_sb00681  lvm2    a--     <136.21g 103.37g    2006    16812               0       free
/dev/sda2   vg_sb00681  lvm2    a--     <136.21g 103.37g    18818   5120    lv_root     0       linear  /dev/sda2:18818-23937
/dev/sda2   vg_sb00681  lvm2    a--     <136.21g 103.37g    23938   1280    lv_home     0       linear  /dev/sda2:23938-25217
/dev/sda2   vg_sb00681  lvm2    a--     <136.21g 103.37g    25218   9651                0       free

Does somebody has any idea or a hint for me?

Answer 1

You'll need pvmove to move the extents around. Since the source and destination are on the same disk, you'll need the --alloc anywhere option:

pvmove --alloc anywhere /dev/sda2:18818-23937 /dev/sda2:2006-7125  # lv_root
pvmove --alloc anywhere /dev/sda2:23938-25217 /dev/sda2:7126-8405  # lv_home

You can do this while the LVs are mounted and in use, just try to avoid doing that while the system is under a heavy disk I/O load.

After these commands, the first free physical extent should be number 8406, and everything from that to the end of the PV should be free, so the PV can now be shrunk.