Hi all,

 I want to ask if it is possible and safe to move online the clustered LV
with GFS on the one PV (multipathed LUN from the old storage) to an other
one (multipathed LUN on the new storage)?

I found these articles in Red Hat knowledgebase:

- Can I perform a pvmove on a clustered logical volume? -
https://access.redhat.com/solutions/39894
- How to migrate SAN LUNs which has Clustered LVM configured on it? -
https://access.redhat.com/solutions/466533

With regard to the mentioned articles it can be done, it is only needed to
install and run the cmirror service. Should I expect any problems or other
prerequisites?


My clustered environment:

- 8 nodes - CentOS 6.9
- LVM version:     2.02.143(2)-RHEL6 (2016-12-13)
  Library version: 1.02.117-RHEL6 (2016-12-13)
  Driver version:  4.33.1
- 7 clustered VGs overall
- 1 LV with GFS mounted on all nodes


- 1 clustered VG with 1 PV and 1 LV on which it is GFS:

[root@...]# pvdisplay /dev/mapper/35001b4d01b1da512
  --- Physical volume ---
  PV Name               /dev/mapper/35001b4d01b1da512
  VG Name               vg_1
  PV Size               4.55 TiB / not usable 2.00 MiB
  Allocatable           yes
  PE Size               4.00 MiB
  Total PE              1192092
  Free PE               1115292
  Allocated PE          76800
  PV UUID               jH1ubM-ElJv-632D-NG8x-jzgJ-mwtA-pxxL90

[root@...]# lvdisplay vg_1/lv_gfs
  --- Logical volume ---
  LV Path                /dev/vg_1/lv_gfs
  LV Name                lv_gfs
  VG Name                vg_1
  LV UUID                OsJ8hM-sH9k-KNs1-B1UD-3qe2-6vja-hLsrYY
  LV Write Access        read/write
  LV Creation host, time ,
  LV Status              available
  # open                 1
  LV Size                300.00 GiB
  Current LE             76800
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           253:418

[root@...]# vgdisplay vg_1
  --- Volume group ---
  VG Name               vg_1
  System ID
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  3898
  VG Access             read/write
  VG Status             resizable
  Clustered             yes
  Shared                no
  MAX LV                0
  Cur LV                1
  Open LV               1
  Max PV                0
  Cur PV                1
  Act PV                1
  VG Size               4.55 TiB
  PE Size               4.00 MiB
  Total PE              1192092
  Alloc PE / Size       76800 / 300.00 GiB
  Free  PE / Size       1115292 / 4.25 TiB
  VG UUID               PtMo7F-XIbC-YSA0-rCQQ-R1oE-g8B7-PiAeIR


- IO activity on the PV (LUN) is very low - from iostat and average per
node: 2.5 tps , 20.03 Blk_read/s and 0 Blk_wrtn/s in 1 minute.


Thank you for your opinions and experience.

Have a great day and with best regards,
-- 
Karel Ziegler