Forum Discussion
The docs say multipathing is not supported for 5.1, but they say they are supported for 6.0 - see extract from 6.0 Linux Bundled Agents Guide:
Linux configuration 3In this example, the volume group testvg_1 is created on disks that have multiplepaths and have LVM tagging enabled.LVMVolumeGroup lvg1 (VolumeGroup = testvg_1EnableLVMTagging = 1)Linux Configuration 4In this example, the volume groups testvg_1 and testvg_2 are created on disksthat have multiple paths. LVM tagging is enabled for testvg_1 and disabled fortest_vg2.
- "The LVMVolumeGroup and the LVMLogicalVolume agents can only be used with the DiskReservation agent"
- Explicity states "Symantec does not support the configuration of logical volumes on disks that have multiple paths" (as a consequence of 1)
The changes in 6.0 are:
- LVMVolumeGroup no longer has to use DiskReservation agent
- Statement saying "Symantec does not support the configuration of logical volumes on disks that have multiple paths" is removed (which I presumed was a consequence of 1 - i.e removal of contraint to use DIskReservtion agent, removes contraint of using single paths)
It could be the examples should say disks using specifically DMP as oppose to any multipathing solution, but, even this been the case, this is just an example - nowhere does it state that multipathing is not supported with LVMVolumeGroup agent. It doesn't explicitly state "LVMVolumeGroup agent supports Multipathing", but it does explicitly state that Diskgroup agent supported Multipathing also.
In any case, I think you are saying 6.0 should not have removed statement "Symantec does not support the configuration of logical volumes on disks that have multiple paths" as multipaths are still not supported in 6.0, but it should technically work, so I will pass this info on to the post https://www-secure.symantec.com/connect/forums/two-node-vcs-linux-cluster-hp-ca-replication which is seeing:
VCS ERROR V-16-10031-14001 (nmsomu01) LVMVolumeGroup:nmsomuVG:online:Activation of volume group failed.
with disks using multiple paths linux device mapper.
I don't understand the rest of what you have said:
We do not design, implement or sell Powerpath, so if it breaks LVM, we should we support it?
No, if powerpath breaks LVM, this is a powerpath or LVM issue, it is nothing to do with VCS - it is only an issue with VCS if you can import a Volume Group manually, but it doesn't online in VCS, but I don't see how this could occur, because agent is running the same command as manual operation.
If the implementation of the product impacts the behaivor of LVM, then we may ask you to remove it and try the cluster LVM agents without the multipathing software.
If a product impacts the behaivor of LVM, then the customer will want to remove (or resolve issue) regardess of whether VCS is installed or not.
Any support for multipathing software will have to come from your vendor as we are only running the base VG commands to import and activate.
Of course, LVM has to support multipathing software, and Linux LVM supports Linux Device Mapper, and as agent is "only running the base VG commands to import and activate", I don't understand why agent cares whether Multipaths are used and why each each multipathing solution needs to be tested and explicitly supported for it to be used.
The bottom line is that multipathing software may break LVM, but this is an issue between LVM and multipathing software and has nothing to do with VCS, but I can't see how multipathing software will change the base VG commands the agents need to run.
Mike
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