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A while back, the behavior of LVM changed from allowing metadata changes when PVs were missing to not allowing changes. Until recently, this change was tolerated by HA-LVM by forcing a 'vgreduce --removemissing' before trying (again) to add tags to an LV and then activate it. LVM mirroring requires that failed devices are removed anyway, so this was largely harmless. However, RAID LVs do not require devices to be removed from the array in order to be activated. In fact, in an HA-LVM environment this would be very undesirable. Device failures in such an environment can often be transient and it would be much better to restore the device to the array than synchronize an entirely new device. There are two methods that can be used to setup an HA-LVM environment: "clvm" or "tagging". For RAID LVs, "clvm" is out of the question because RAID LVs are not supported in clustered VGs - not even in an exclusively activated manner. That leaves "tagging". HA-LVM uses tagging - coupled with 'volume_list' - to ensure that only one machine can have an LV active at a time. If updates are not allowed when a PV is missing, it is impossible to add or remove tags to allow for activation. This removes one of the most basic functionalities of HA-LVM - site redundancy. If mirroring or RAID is used to replicate the storage in two data centers and one of them goes down, a server and a storage device are lost. When the service fails-over to the alternate site, the VG will be "partial". Unable to add a tag to the VG/LV, the RAID device will be unable to activate. The solution is to allow vgchange and lvchange to alter the LVM metadata for a limited set of options - --[add|del]tag included. The set of allowable options are ones that do not cause changes to the DM kernel target (like --resync would) or could alter the structure of the LV (like allocation or conversion).