2.6. Storage Metadata Versions in Red Hat Virtualization

Red Hat Virtualization stores information about storage domains as metadata on the storage domains themselves. Each major release of Red Hat Virtualization has seen improved implementations of storage metadata.
  • V1 metadata (Red Hat Virtualization 2.x series)
    Each storage domain contains metadata describing its own structure, and all of the names of physical volumes that are used to back virtual disks.
    Master domains additionally contain metadata for all the domains and physical volume names in the storage pool. The total size of this metadata is limited to 2 KB, limiting the number of storage domains that can be in a pool.
    Template and virtual machine base images are read only.
    V1 metadata is applicable to NFS, iSCSI, and FC storage domains.
  • V2 metadata (Red Hat Enterprise Virtualization 3.0)
    All storage domain and pool metadata is stored as logical volume tags rather than written to a logical volume. Metadata about virtual disk volumes is still stored in a logical volume on the domains.
    Physical volume names are no longer included in the metadata.
    Template and virtual machine base images are read only.
    V2 metadata is applicable to iSCSI, and FC storage domains.
  • V3 metadata (Red Hat Enterprise Virtualization 3.1+)
    All storage domain and pool metadata is stored as logical volume tags rather than written to a logical volume. Metadata about virtual disk volumes is still stored in a logical volume on the domains.
    Virtual machine and template base images are no longer read only. This change enables live snapshots, live storage migration, and clone from snapshot.
    Support for unicode metadata is added, for non-English volume names.
    V3 metadata is applicable to NFS, GlusterFS, POSIX, iSCSI, and FC storage domains.