How to convert striped LV to linear LV

Solution Verified - Updated -

Environment

  • Redhat Enterprise Linux 5.8 and later
  • LVM2

Issue

  • How to convert striped LV to linear LV within the logical volume manager ?
  • Is it possible to convert an LVM striped logical volume to a linear/concatenated logical volume ?

Resolution

  • Below are the steps to convert striped LV to Linear LV.

  • There is no direct command to convert striped LV to Linear. First you need to convert it to a mirrored volume and then to a Linear volume.

  • First add a PV to the existing VG

    # lvs -a -o +devices
  stripelv stripevg   -wi-a-   7.47G         /dev/hdb1(0),/dev/hdb2(0),/dev/hdb3(0),/dev/hdb4(0)

# pvcreate /dev/hdd1
  Writing physical volume data to disk "/dev/hdd1"
  Physical volume "/dev/hdd1" successfully created

# vgextend stripevg /dev/hdd1
  Volume group "stripevg" successfully extended

# vgs
  VG         #PV #LV #SN Attr   VSize  VFree 
  VolGroup00   1   2   0 wz--n- 14.88G     0 
  stripevg     5   1   0 wz--n- 21.45G 13.98G

  • Then convert the striped LV to mirrored LV.

    # lvconvert -m 1 stripevg/stripelv
Insufficient suitable allocatable extents for logical volume : 1912 more required
Unable to allocate extents for mirror(s).

  • If you get the above error, add another physical device to the Volume group so that the logs can be kept on the disk and then try to run the lvconvert command.

  • The log can also be kept in memory with the --mirrorlog core option so that no extra physical volume is needed to mirror the device.

    # lvconvert --mirrorlog core -m 1 stripevg/stripelv
stripevg/stripelv: Converted: 0.0%
stripevg/stripelv: Converted: 1.2%
stripevg/stripelv: Converted: 2.4%
stripevg/stripelv: Converted: 3.5%
.
.
stripevg/stripelv: Converted: 97.0%
stripevg/stripelv: Converted: 98.0%
stripevg/stripelv: Converted: 99.1%
stripevg/stripelv: Converted: 100.0%
[root@localhost ~]#

  • Once the mirror is completed successfully verify it as below.

    # lvs -a -o +devices
LV                  VG         Attr   LSize   Origin Snap%  Move Log Copy%  Convert Devices                                            
stripelv            stripevg   mwi-a-   7.47G                        100.00         stripelv_mimage_0(0),stripelv_mimage_1(0)          
[stripelv_mimage_0] stripevg   iwi-ao   7.47G                                       /dev/hdb1(0),/dev/hdb2(0),/dev/hdb3(0),/dev/hdb4(0)
[stripelv_mimage_1] stripevg   iwi-ao   7.47G                                       /dev/hdd1(0)

  • Then convert the mirrored LV to linear LV with the below command.

    #lvconvert -m 0 stripevg/stripelv /dev/hdb1 /dev/hdb2 /dev/hdb3 /dev/hdb4
Logical volume stripelv converted.
[root@localhost ~]# 
[root@localhost ~]#

  • Verify with the below command.

    # dmsetup table | grep stripelv
stripevg-stripelv: 0 15663104 linear 22:65 384

    Or with

    # lvdisplay

Root Cause

  • There is not direct command to convert a Striped LV to Linear LV. First you need to convert it to a mirrored LV and then to a Linear LV.

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