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

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• Auto pre-allocation
Indicates whether the automatic increase of pre-allocated extents is enabled or not. This is displayed
only for space efficient snapshots beginning with the HP-UX 11i v3 September 2010 Update
release.
• Threshold Percent
Displays the threshold percentage at which increment messages are logged in syslog and the
automatic increase of pre-allocated is triggered. This is displayed only for space efficient snapshots
beginning with the HP-UX 11i v3 September 2010 Update release.
Beginning with the HP-UX 11iv 3 September 2010 Update release, the Distribution of logical
volume section has the following changes:
• It displays only the Unshared LE and Unshared PE fields for space efficient snapshots. In the
HP-UX 11i v3 March 2010 Update release, the LE on PV, PE on PV, Unshared LE, and
Unshared PE fields were displayed for space-efficient and fully-allocated snapshots.
• It is not displayed for a space-efficient snapshot if it does not have any unshared extents.
Example 1: Space-efficient snapshot logical volume
The following lvdisplay verbose output shows a space-efficient snapshot of logical volume
/dev/vg01/lvol1. The snapshot status is operative and it is a mirrored snapshot. It has 50
pre-allocated logical extents, of which two logical extents have been unshared and the rest are
represented by Current pre-allocated LE. The corresponding number of physical extents is
represented by Current pre-allocated PE.
Because the snapshot is mirrored, its unshared extents are mapped to two physical volumes (shown in
the Distribution of logical volume section). The logical extent to physical extent mapping for the
unshared extents is shown in the Unshared Logical extents section. The extents that are pre-
allocated are shown in Pre-allocated extents. For each pre-allocated logical extent of the
snapshot, there are two physical extents because the space-efficient snapshot is mirrored.
# lvdisplay -v /dev/vg01/lvol1_S2
--- Logical volumes ---
LV Name /dev/vg01/lvol1_S2
VG Name /dev/vg01
LV Permission read/write
LV Status available/syncd, snapshot,space efficient
Snapshot Status operative
Mirror copies 1
Consistency Recovery MWC
Schedule parallel
LV Size (Mbytes) 1024
Current LE 128
Allocated PE 4
Stripes 0
Stripe Size (Kbytes) 0
Bad block NONE
Allocation strict
IO Timeout (Seconds) default
Pre-allocated LE 50
Current pre-allocated LE 48
Unshared LE 2
Current pre-allocated PE 96
Original LV /dev/vg01/lvol1
Timestamp Tue Jan 26 17:57:43 2010
Auto Pre-allocation Enabled
Threshold Percent 50