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Expanding LVM storage repository by adding extra drives (worked example)

Lenovo/IBM ServeRAID M5210 supports online capacity expansion to increase the size of a virtual drive. Unfortunately, this is not supported for RAID 10. To avoid having to destroy the virtual drive and recreate at a larger size (thus losing all data in the process), it is possible to add create an extra virtual drive and add that capacity to the storage repository.

1. Create the new virtual drive using your on-line or off-line RAID management
2. Look at dmesg to find the virtual drive, in this case /dev/sdd:

   [  259.157164] scsi 0:2:2:0: Direct-Access     IBM      ServeRAID M5210  4.68 PQ: 0 ANSI: 5
   [  259.157573] sd 0:2:2:0: [sdd] 1951170560 512-byte logical blocks: (999 GB/930 GiB)
   

3. Run nano /etc/lvm/lvm.conf. Press Ctrl-W and search for metadata_read_only. Alter the metadata_read_only = 1 line to read metadata_read_only = 0 and type Ctrl-X to save:

           # Configuration option global/metadata_read_only.
           # No operations that change on-disk metadata are permitted.
           # Additionally, read-only commands that encounter metadata in need of
           # repair will still be allowed to proceed exactly as if the repair had
           # been performed (except for the unchanged vg_seqno). Inappropriate
           # use could mess up your system, so seek advice first!
           metadata_read_only = 0
   

4. Create your new PV with pvcreate following by the device you determined above. You can check with pvdisplay:

   [root@xenserver01 ~]# pvcreate /dev/sdd
     Physical volume "/dev/sdd" successfully created
   [root@xenserver01 ~]# pvdisplay
   # 
     --- Physical volume ---
     PV Name               /dev/sdc
     VG Name               VG_XenStorage-7299b4da-46fd-d088-a909-1d040f6a859c
     PV Size               2.00 TiB / not usable 12.00 MiB
     Allocatable           yes
     PE Size               4.00 MiB
     Total PE              524285
     Free PE               52450
     Allocated PE          471835
     PV UUID               UxN4ao-U7iO-4QLN-qxXs-d4gQ-0ifU-bj77aZ
   
     --- Physical volume ---
     PV Name               /dev/sdb
     VG Name               XSLocalEXT-3ad7ce7b-5545-f170-6a86-29eb746dc8e2
     PV Size               446.10 GiB / not usable 13.00 MiB
     Allocatable           yes (but full)
     PE Size               4.00 MiB
     Total PE              114199
     Free PE               0
     Allocated PE          114199
     PV UUID               UGJjrE-yx3d-erTu-Koid-qp2E-Y0eo-t9R0Vb
   
     --- Physical volume ---
     PV Name               /dev/sda3
     VG Name               VG_XenStorage-ec222c87-7812-7ff4-5d3d-5da65664f7b0
     PV Size               1.78 TiB / not usable 14.98 MiB
     Allocatable           yes
     PE Size               4.00 MiB
     Total PE              465732
     Free PE               189741
     Allocated PE          275991
     PV UUID               hCriEm-GfqF-hr0u-G0sr-WOYZ-dtLe-gPnj4E
   
     "/dev/sdd" is a new physical volume of "930.39 GiB"
     --- NEW Physical volume ---
     PV Name               /dev/sdd
     VG Name
     PV Size               930.39 GiB
     Allocatable           NO
     PE Size               0
     Total PE              0
     Free PE               0
     Allocated PE          0
     PV UUID               jbOvYD-rKSy-aQJk-c9gP-QoOP-YNp5-3QeMPQ
   

5. Determine the UUID of the SR you want to expand (in this case Local storage):

   [root@xenserver01 ~]# xe sr-list name-label=Local\ storage
   uuid ( RO)                : ec222c87-7812-7ff4-5d3d-5da65664f7b0
             name-label ( RW): Local storage
       name-description ( RW):
                   host ( RO): xenserver01
                   type ( RO): lvm
           content-type ( RO): user
   

6. View the current properties using vgdisplay by appending the SR UUID onto VG_XenStorage-:

   [root@xenserver01 ~]# vgdisplay VG_XenStorage-ec222c87-7812-7ff4-5d3d-5da65664f7b0
     --- Volume group ---
     VG Name               VG_XenStorage-ec222c87-7812-7ff4-5d3d-5da65664f7b0
     System ID
     Format                lvm2
     Metadata Areas        1
     Metadata Sequence No  9158
     VG Access             read/write
     VG Status             resizable
     MAX LV                0
     Cur LV                38
     Open LV               0
     Max PV                0
     Cur PV                1
     Act PV                1
     VG Size               1.78 TiB
     PE Size               4.00 MiB
     Total PE              465732
     Alloc PE / Size       275991 / 1.05 TiB
     Free  PE / Size       189741 / 741.18 GiB
     VG UUID               GzfTxt-NYud-uajR-fZZ5-hCo5-jSrQ-VqeWI0
   

7. Extend the VG using vgextend using the VG name and device name as arguments:

   [root@xenserver01 ~]# vgextend VG_XenStorage-ec222c87-7812-7ff4-5d3d-5da65664f7b0 /dev/sdd
     Volume group "VG_XenStorage-ec222c87-7812-7ff4-5d3d-5da65664f7b0" successfully extended
   [root@xenserver01 ~]# vgdisplay VG_XenStorage-ec222c87-7812-7ff4-5d3d-5da65664f7b0
     --- Volume group ---
     VG Name               VG_XenStorage-ec222c87-7812-7ff4-5d3d-5da65664f7b0
     System ID
     Format                lvm2
     Metadata Areas        2
     Metadata Sequence No  9159
     VG Access             read/write
     VG Status             resizable
     MAX LV                0
     Cur LV                38
     Open LV               0
     Max PV                0
     Cur PV                2
     Act PV                2
     VG Size               2.69 TiB
     PE Size               4.00 MiB
     Total PE              703911
     Alloc PE / Size       275991 / 1.05 TiB
     Free  PE / Size       427920 / 1.63 TiB
     VG UUID               GzfTxt-NYud-uajR-fZZ5-hCo5-jSrQ-VqeWI0
   

8. Rescan the SR either from XenCenter or from the CLI:

   [root@xenserver01 ~]# xe sr-scan uuid=ec222c87-7812-7ff4-5d3d-5da65664f7b0
   

9. Revert your changes to lvm.conf by running nano /etc/lvm/lvm.conf. Press Ctrl-W and search for metadata_read_only. Alter the metadata_read_only = 0 line to read metadata_read_only = 1 and type Ctrl-X to save