RHV: Hosts boot with Guest LVs activated

Issue

• Guest Logical Volumes (LVs) activated when host is rebooted, leading to stale LVs.

• On the host, LVM sees all the LVs of the storage domain(s), scans all these devices and finds any LVM metadata that exists inside a guest, if the guest's Volume Group was created inside a raw disk. Then it activates and opens the VM's LVs on the host. The device-mapper devices that are created on the host for the guest's LVs result in the VM's LVs not being able to be deactivated or removed, ending up with stale LVs, which can lead to several other issues, including data corruption.

• The host takes too long to boot.

• The criteria for encountering this are:

  • The storage domain is of type Block, such as FibreChannel or iSCSI. VM's disk created in this storage domain is Preallocated.
    • Or a Direct LUNs
  • Within the Guest, a PV, VG and at least one LV are created inside the full disk, i.e. not in a disk partition.
    • Within the Guest, creating the PV on top of a partitioned device (i.e.: vda1, vdb2) avoids this problem.
    • Within the Guest, creating the PV on top of a whole block device (i.e.: vda, vdb) makes the Guest susceptible to this problem.
  • If a snapshot is taken that includes the preallocated disk, the resultant active volume will be thin-provisioned. If the VG is created after the snapshot was taken, then the problem described here will not occur. If the VG was created before the first snapshot was taken, the problem will occur.