WARNING: PV /dev/sdX in VG vgXX is using an old PV header, modify the VG to update

Root Cause

• The root cause is the pv_header_extension.version field in RHEL8 environment is expected match the current PV_HEADER_EXTENSION_VSN (2), but does not:

  # pvck --dump headers /dev/<device-named-in-warning-message>
  :
    pv_header_extension.version 1    <==== out of date version, old structure format.
  

• These warnings come continuously when a device is moved directly from RHEL version 5 to 8 system without exporting/importing a VG. Every time an lvm command is run, warnings will be generated.

• These warnings appear when a device moves from RHEL 5 to 6 then RHEL 6 to 7 and finally to RHEL 8.

  • The pv_header_extension lvm2 data structure was not present in RHEL 5.

  • The pv_header_extension lvm2 data structure was added in RHEL 6 with a version number of '1':

      File         Function    Line
    0 layout.h     <global>     26 #define PV_HEADER_EXTENSION_VSN 1
    1 text_label.c _text_write 126 pvhdr_ext->version = xlate32(PV_HEADER_EXTENSION_VSN);
    
    #define PV_HEADER_EXTENSION_VSN 1
    struct pv_header_extension {
            uint32_t version;
            uint32_t flags;             <== unused flags, no values defined.
            /* NULL-terminated list of bootloader areas */
            struct disk_locn bootloader_areas_xl[0];
    } __attribute__ ((packed));
    

  • The current pv_header_extension had its version number increased to '2' within RHEL 7.9 release when the flags entry within the above structure had changes to its flags value (in RHEL6 that field was not used). However, there was no uniform method of detecting old LVM2 metadata version information within the pv_header_extension within RHEL 7 and notifying users.

    /*
     * PV header extension versions:
     *   - version 1: bootloader_areas_xl support (flags unused)
     *   - version 2: PV_EXT_USED flags support added
     */
    #define PV_HEADER_EXTENSION_VSN 2
    struct pv_header_extension {
            uint32_t version;             <=== expected to be '2'
            uint32_t flags;               <=== flags used
            /* NULL-terminated list of bootloader areas */
            struct disk_locn bootloader_areas_xl[0];
    } __attribute__ ((packed));
    

  • Within RHEL 8, the LVM2 metadata checks performed on PVs was separated from other code paths and re-written to provide more consistent warnings when on-disk metadata failed sanity checks, including checking the value of pv_header_extension.version field.

     [...]
       69                 ext_version = lvmcache_ext_version(info); 
       70                 if (ext_version < PV_HEADER_EXTENSION_VSN) {            <<< Current version is '2'
       71                         log_warn("WARNING: PV %s in VG %s is using an old PV header, modify the VG to update.",
       72                                  dev_name(pvl->pv->dev), vg->name);     <<< printed here 
       73                         continue;
       74                 }
       75 
     [...]
    

• The recommended way of moving a data VG is using vgexport/vgimport. You may refer to "How do I move a Volume Group from one system to another?" for additional information.