11-15-2002
With physical partitions, a disk is subdivided into partitions. And somehow the disk driver knows about the subdivision scheme. The driver may read a table off the first sector of the disk. Or the driver may just get the model number of the drive and pick a built-in table. The special files are named to indicate the section. c0t0d0s2 would be section "2" of the disk (which was always the whole thing).
With logical volumes, a disk like c0t0d0s2 (or maybe just c0t0d0 theses days) is just a physical volume which gets tossed into a pool called a volume group. Then you have very great flexibility in creating logical volumes. A logical volume may be a very small slice of a disk. Or it may be so large that it is several disk drives.
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LEARN ABOUT REDHAT
vgscan
VGSCAN(8) System Manager's Manual VGSCAN(8)
NAME
vgscan - scan all disks for volume groups and build /etc/lvmtab and /etc/lvmtab.d/* which are the database for all other lvm commands.
SYNOPSIS
vgscan [-d|--debug] [-f|--forcenumbers] [-h|--help] [-r|--remove_snapshots [VolumeGroupName]] [-v|--verbose]
DESCRIPTION
vgscan scans all SCSI, (E)IDE disks, multiple devices and a bunch of other disk devives in the system for volume groups defined.
OPTIONS
-d, --debug
Enables additional debugging output (if compiled with DEBUG).
-f, --forcenumbers
If used volume group and/or logical volume minor numbers are found during scan, replace them. This will potentially cause problems
for NFS exported filesystems on logical volumes with changed numbers.
-h, --help
Print a usage message on standard output and exit successfully.
-r, --remove_snapshots [VolumeGroupName]
Remove all snapshot logical volumes from all or just the named volume group.
-v, --verbose
Display verbose information of vgscan's activities.
Hint
Put vgscan in one of your system startup scripts. This gives you an actual logical volume manager database before activating all volume
groups by doing a "vgchange -ay".
DIAGNOSTICS
vgscan returns an exit code of 0 for success and > 0 for error:
1 error reading physical volumes
2 error inserting vokume group name into lvmtab
3 no volume group(s) found
4 error creating lvmtab
5 no or not enough free device specials to store volume group in lvmtab
6 error storing VGDA on disk(s)
7 reused LV device number
8 error releasing snapshot logical volume
95 driver/module not in kernel
96 invalid I/O protocol version
97 error locking logical volume manager
99 invalid command line
See also
lvm(8), vgcreate(8), vgchange(8)
AUTHOR
Heinz Mauelshagen <Linux-LVM@Sistina.com>
Heinz Mauelshagen LVM TOOLS VGSCAN(8)