VERITAS Volume Manager 3.5 Migration Guide (August 2002)

Coexistence of VxVM and LVM Disks Final 24 July 2002
6 VERITAS Volume Manager Migration Guide
Coexistence of VxVM and LVM Disks
Both LVM disks and VxVM disks can exist together on a system. The LVM disks are
detected and displayed as such by VxVM. LVM disks are not selected by VxVM for
initialization, addition, or replacement.
Mirrors Mirrors (Plexes)
Both LVM and VxVM support mirrors. Mirrors can be used to store multiple copies of a volume’s
data on separate disks.
In LVM, you can create mirrors usingthe MirrorDisk/UX product. Mirrors allowduplicate copies
of the extents to be kept on separate physical volumes. MirrorDisk/UX supports up to 3 copies of
the data.
A VxVM mirror consists of plexes. Each plex is a copy of the volume. A plex consists of one or
more subdisks located on one or more disks. VxVM volumes can have up to 32 mirrors (where
each plex is a copy of data). Mirroring features are available with an additional license.
Export Deport
In LVM, exporting removes volume group information from /etc/lvmtab. The volume group
must have already been deactivated.
Similarly in VxVM, deport makes a disk group inaccessible by the system.
Import Import
In LVM, import adds a volume group to the system and the volume group information to
/etc/lvmtab but does not make the volumes accessible. The volume group must be activated by
the vgchange -a y command in order to make volumes accessible.
In VxVM, import imports a disk group and makes the diskgroup accessible by the system.
Bad Block Pool No similar term
In LVM, the bad block pool provides for the transparent detection of bad disk sectors, and the
relocation of data from bad to good disk sectors. The bad block reallocation feature does not exist
in VxVM because the vectoring of bad blocks is now done by most hardware.
/etc/lvmtab No similar term
/etc/lvmtab is a file that contains information about volume groups that are accessible by a
system.
Table 1. A Conceptual comparison of LVM and VxVM
LVM Term VxVM Term