HP-UX 11i v3 Using LVM Logical Volume Snapshots (September 2010)

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LV Name /dev/vg01/lvol1_S3
LV Status available/syncd, snapshot,fully allocated
Snapshot Status operative
LV Size (Mbytes) 1024
Current LE 128
Allocated PE 128
Unshared LE 0
Used PV 1
--- Physical volumes ---
PV Name /dev/disk/disk15476
PV Status available
Total PE 2524
Free PE 2218
Current pre-allocated PE 48
Autoswitch On
Proactive Polling On
PV Name /dev/disk/disk15820
PV Status available
Total PE 2524
Free PE 2474
Current pre-allocated PE 48
Autoswitch On
Proactive Polling On
pvdisplay command
The following new fields are added in the pvdisplay output for snapshot logical volumes:
• Current pre-allocated PE
Displays the total number of physical extents of the physical volume that are present in the
pre-allocated pool of any of the snapshot logical volumes of the volume group.
• Unshared LE on LV
Represents the number of logical extents of each snapshot logical volume in the volume group that
have been unshared to an extent on this physical volume. This field is displayed in pvdisplay
verbose output in the distribution of physical volumes section.
• pre-allocated status
A new status in the Physical Extents section. Indicates those extents of the physical volume that
are currently present in the pre-allocated pool, but have not been unshared. The snapshot logical
volume to which these extents are mapped is also displayed for each such extent. The logical extent
number is set to NO_LXINDEX to indicate that these extents are not yet mapped to a logical extent,
but have been set aside for a future unshare operation.
The following pvdisplay verbose output shows a physical volume with a total of 48 pre-allocated
extents. The physical volume has its extents mapped to the logical extents of the original logical
volume and both its snapshots. Two physical extents of this physical volume are mapped to unshared
extents of the space-efficient snapshot /dev/vg01/lvol1_S2. No physical extent of the physical
volume is mapped to any unshared extent of the fully-allocated snapshot /dev/vg01/lvol1_S3.
The partial output of the physical extent to logical extent map shows that physical extents 128 and
129 are mapped to unshared logical extents 0 and 1 of the space-efficient snapshot
/dev/vg01/lvol1_S2 and the remaining physical extents from 132 to 177 are pre-allocated.
Because pre-allocated extents are not mapped to any logical extents, the logical extent number is
shown as NO_LXINDEX. Physical extents from 178 to 305 are mapped to the fully-allocated
snapshot; the physical extents that follow are free.