Veritas Storage Foundation 5.1 SP1 Advanced Features Administrator"s Guide (5900-1503, April 2011)

Another factor in converting stripes is that stripes create more work for the
converter. In some cases, stripes require 1GB volume, although only the
metadata is being changed. In other cases, where there are more physical disks
in one volume than another, there is more metadata to deal with. The converter
has to read every physical extent map to ensure there are no holes in the
volume; if holes are found, the converter maps around them.
■ Number of volumes. While it takes longer to convert one 64GB volume than
one 2GB volume, it also takes longer to convert 64 1GB volumes than one 64GB
volume, providing that the volumes are of similar type.
■ Mirrored volumes. Mirrored volumes typically do not take more time to convert
than simple volumes. Volumes that are mirrored and striped at the same time
would take longer, but LVM currently does not allow this.
Currently, after conversion, mirrored volumes are not automatically
synchronized because a large mirror could take hours to complete.
For example, in tests, a 150GB volume group consisting of 20 simple logical
volumes takes approximately 35-40 minutes to convert. In contrast, the same
volume group (150GB) consisting of mirrored volumes that need to be
synchronized can take 30-40 hours to convert.
Note: If you convert mirrored volumes, you must synchronize them in a separate
step.
Non-interactive conversion of volume groups
The vxvmconvert utility is an interactive command. You can also use the
vxautoanalysis command and the vxautoconvert command to perform
non-interactive analysis and conversion of LVM volume groups. The
vxautorollback command also lets you reverse the conversion, and turn a VxVM
disk group back into an LVM volume group.
Analyzing volume groups for conversion
The vxautoanalysis utility analyses one or more LVM volume groups, and reports
on their suitability for conversion to VxVM disk groups. Only analysis of the
suitability of the volume groups for conversion is performed. The actual conversion
can be performed by using the vxautoconvert utility or the vxvmconvert utility.
Note: The VxVM configuration daemon (vxconfigd) must be running in order for
the analysis to succeed.
Offline data migration
Converting LVM to VxVM
432