Veritas Volume Manager 5.0 Migration Guide, HP-UX 11i v3, First Edition, May 2008

18 Converting LVM to VxVM
Converting LVM volume groups to VxVM disk groups
Volume group conversion limitations
There are certain LVM volume configurations that cannot be converted to
VxVM. Some of the reasons a conversion could fail are:
■ A volume group with insufficient space for metadata.
In the conversion of LVM to VxVM, the areas of the disks used to store LVM
metadata are overwritten with VxVM metadata. If the VxVM metadata that
needs to be written will not fit the space occupied by the LVM metadata, the
group containing the disk cannot be converted. If you have just enough
space for the conversion, you probably would want to have more space for
future configuration changes.
Note: The most likely scenario in which a Volume Group cannot be
converted, because of insufficient private space, is when a large HP-UX
system using “Extent based Striping” is being used
■ A volume group containing the root volume.
vxvmconvert does not convert any volume group that contains a rootable
volume, identified by the presence of the LIF area as created by
mkboot(1M).
Not only is the current root volume off limits, but any volume that might be
used as an alternate root volume is rejected as well.
Note: You can use the vxcp_lvmroot(1M) command to create a VxVM root disk
on a spare physical disk from the contents of the existing LVM root disk.
Similarly, you can use the
vxres_lvmroot(1M) command to recreate an LVM
root disk on a spare disk from the contents of the VxVM root disk. For more
information, see the section “Rootability” in the “Administering Disks” chapter
of the Veritas Volume Manager Administrator’s Guide.
■ A volume group containing mirrors using the Mirror Write Cache feature for
volume consistency recovery.
Users should be aware that when converting mirrored LVM volumes to
VxVM, some of these volumes will likely have the Mirror Write Cache
consistency recovery method in force on the volume. The
vxvmconvert
utility can convert these volumes, but must use the Dirty Region Logging
(DRL) feature to obtain the same level of functionality. However, since Dirty
Region Logging requires some user space to be available for the log, a
conversion could fail due to an MWC volume being full, leaving no space for
the DRL log. However it is very unlikely that this situation would occur.
Note that the MWC and DRL are used only when the system crashes or is
improperly shut down, to quickly bring all mirrors in the volume back into a
consistent state.