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Logical Volume Manager

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Logical volume manager.

Logical Storage :  AIX works with logical storage LVM manages/maps the logical storage to
the physical storage

Features
1) No need to be contiguous disk space
2) span multiple disk
3) mirroring
4) lv can be relocated.

VGDA (Volume Group Descriptor Area) Stores structural information about the LVM
You will find this on every disk part of the LVM

/etc/filesystems

Physical Volume PV   :    Hard disk
Volume Groups  VG    :   Grouping of Hard Disk or PV, we have two types 
                                     Regular which has max of 32 PV and Big VG which  has 128 PV
Physical Partition  PP  :  Every Disk or PV part of a VG is divided into PP of same size
Logical Partition  LV     :  This are the pointers to the Physical Partition
Logical Volume LV       :  This are the grouping of the Logical Partition

Mirroring : Here we have one or more copies of a Logical Volume
i.e the LP of the LV are pointing to  more than one PP

2PP       1 LP
3PP       1 LP

Striping

Data is stripped and is written across multiple disks in the
striped logical volume

Basic Commands

#lsfs .

list definition about your file system size is in  512 Bytes
i.e gives list of LV in the VG


#lsvg list all volume group

#lsvg rootvg ; List information about CG
                    PP Size in MB
                    Total PP Number of Physical partion in vg
                    Free PP  Number of Unallocated PP

#lsvg -p rootvg

List all PV in the VG



#lsvg -l rootvg

#lspv  :list all physical volume and their alloction on disk

outer edge,middle edge,center,middle innder edget,inner edge


#lsvg -o : // list active vg




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Disk Management.

#uname -m
First Eight are Machine ID
<xxxxxxx><xxxx>
<Machine Id><Type>


#lspv
<machine id><date time of volume configured>



VGDA (Volue Group Descriptor Area)

Header Time stamp : Timestamp of last VG modification
Physical Volume List
Logical Volume List
Physical Partition Map


Most important data structure of LVM
All the administrative information about the Volume group

VGSA  (Volume Group Status Area)
Tracks the state of mirrored copies


LVCB (Logical Volume Control Block)


Files where the LVM info is stored
/etc/vg/vg-id
/dev/hdiskX
/dev/VGname
/dev/LVname
/dev/filesystem


To display information about logical volume dbdata1, enter:

#lslv dbdata1

To display information about logical volume dbdata1 by physical volume, enter:

#lslv -l dbdata1

To display the logical volume allocation map for hdisk2, enter:

#lslv -p hdisk2

To see the placement of the partitions of logical volume dbdata1 within physical volume hdisk0, use the following:
# lslv -p hdisk0 dbdata1
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