vgexport with cluster nodes

[himacs]

Hi Admins,

Whats the exact reason used -s option with vgexport while exporting VG map file.As i know -s option will generate VGID with map file.

My assumption:

We will be creating new VG before importing on node 2.So imported map file with VGID will set the new VGID for newly created VG.


Please help on understanding this.

Regards
himacs

[Torsten.]

The system "knows" easily which disk belongs to the VG in question because all have the same vgid.

[Mel Burslan · Accepted solution]

From the man pages of vgexport:

-s Sharable option, Series 800 only. When the -s
option is specified, then the -p, -v, and -m
options must also be specified. A mapfile is
created that can be used to create volume group
entries on other systems in the high availability
cluster (with the vgimport command).


As you can see, -s is not the reson you are getting a map file. It is the sharable VG flag being set and that is only required for series 800 machines (quite old).

Otherwise, mapfile does not necessarily give you the VGID information. Mapfile contains the lvol sequence numbers when importing it on another system. VGID does not get set in the vgexport and vgimport process. Actually, the whole process depends on the consistent VGID information to be recorded on each LUN making up this volume group.

Hope this helps

[Stephen Doud]

/etc/lvmtab is used by LVM during VG activation. lvmtab must reference the correct /dev/dsk/c-t-d- device special files (DSFs) that match the PVs that are assigned to a volume group so that volume group activation occurs properly.

When an admin creates a volume group on one server, /etc/lvmtab is loaded with DSF references that may not be the same references on other nodes in the cluster (if the LUN is shared/seen by the other nodes). To insure the correct DSFs are loaded, the -s option is used during preview vgexport, along with -m and to load the assigned VGID for the volume group, into the map file. The usefulness is apparent when the vgimport is performed on another node, where the same map file is referenced and the -s option is used.
This causes the other node to inspect the LVM metadata on each disk, looking for those that have a matching VGID, and if matching, the DSF for that path is loaded into /etc/lvmtab. The helps insure the correct DSFs are loaded into the other node's /etc/lvmtab.

[himacs]

Hi Thanks for the info.

-s parameter helps the LVM to load the correct PVs into lvmtab on cluster env.

Regards
himacs