UPDATE: Hoarders and chuckers (Reconstructing a VG)
AnthonyEnglish 270000RKFN Comments (4) Visits (8293)
It's pretty easy to move a volume group from one AIX system to another. You unmount all the file systems from the source volume group, varyoff the VG, export the volume group (exportvg), and then remove the disks from the source system (rmdev -dl hdiskN). Then you assign the LUNs to the target host, import the volume group, mount the file systems, and check permissions.
But what if you want to copy a volume group? You might want to replicate a volume group, by doing a flash copy across the SAN. Then on the remote site, you'd present the SAN LUNs to the target host, run cfgmgr to get the host to see the new disks. The disks on the source host may be named differently on the target host, because the target will just assign the next available hdisk number when you run the cfgmgr. The hdisk numbers may be different between the source and target hosts, but the Physical Volume IDs are the same. After all, the target LUN is a replica of the source LUN.
The problem: duplicate PVIDs and LVs
But that brings up a problem: duplicate PVIDs.
Enter the recreatevg command. Just like the move you can do with importvg and varyonvg,
That overcomes the issue of duplicate PVIDs and Logical Volume IDs.
Now when you run the importvg command yourself, you only specify one physical volume. For example, if the volume group consists of hdisk1, hdisk2 and hdisk3, then the command
importvg -y datavg hdisk2
will import the entire volume group, since the Volume Group Descriptor Area (VGDA) is on all three disks, and all the disks in the volume group know the PVIDs of all the other disks in that volume group.
When you run recreatevg,
So if you're wondering why the logical volumes on the disks you forgot to mention didn't get included, the LVM will reply: "you never asked." I expect that's because recreatevg (unlike importvg), isn't relying on PVIDs, since it's creating new ones.
Update: Hoarders and chuckers
There are two kinds of people in the world. Some like to keep their old junk, just in case they'll need it some day (they won't!). Others like to toss it out, just in case they don't need it (they will!). The first are the hoarders, the second are those who are chuckers (with apologies to our cultured readership for using such an expression). Well, importvg is a hoarder: you nominate one disk and it assumes you want the others in the volume group. recreatevg, on the other hand, is a chucker.
Perhaps people with more experience using recreatevg will have comments about how this all works in the real world (the recreatevg command, not how to keep the peace between hoarders and chuckers).