Vgextend fails with error "Devices have inconsistent logical block sizes" when trying to add a VDO device.

Solution Verified - Updated -

Environment

  • Red Hat Enterprise Linux 7
  • Red Hat Enterprise Linux 8
  • VDO

Issue

  • Unable to extend the VG using VDO device. Getting error as:
[root@rhel8 test4]# vgextend vg1 /dev/mapper/vdo4 
 Devices have inconsistent logical block sizes (512 and 4096).
  • vgextend fails due to inconsistent block size of the underline physical volume on sd device and VDO device.

Resolution

  • By default, allow_mixed_block_sizes is disabled. Enable allow_mixed_block_sizes in lvm.conf file in order to allow the same VG to have two PV with different block sizes:
[root@rhel8 test4]# cat /etc/lvm/lvm.conf | grep -i "allow_mixed_block_sizes" | grep -v "#"
    allow_mixed_block_sizes =1
  • The default logical block size of VDO is 4096K (8 Sectors).

Root Cause

  • By default, the same logical block size is allowed for a VG for two different PV's. To use two different block sizes in same VG, enable allow_mixed_block_sizes in lvm.conf file.

Diagnostic Steps

  • Verify the value set for allow_mixed_block_sizes in lvm.conf:
[root@rhel8 test4]# cat /etc/lvm/lvm.conf | grep -i "allow_mixed_block_sizes" | grep -v "#"
    allow_mixed_block_sizes =0
  • Verify the block size of a disk by using parted or sg_readcap command:
[root@rhel8 test4]# parted /dev/sdb u s p                         
Model: VMware Virtual disk (scsi)
Disk /dev/sdb: 20971520s
Sector size (logical/physical): 512B/512B   <<<<< Sector Size
Partition Table: msdos
Disk Flags: 

Number  Start  End  Size  Type  File system  Flags

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