HP-UX HB v13.00 Ch-13 - LVM

HP-UX Handbook – Rev 13.00 Page 98 (of 110)
Chapter 13 LVM
October 29, 2013
round-robin order on the list of available physical volumes.
The distributed allocation policy REQUIRES the PVG-strict allocation policy (-s
g) to ensure that mirrors of distributed extents do not overlap (for maximum
availability).
lvcreate(1M) will obtain the list of available physical volumes
from /etc/lvmpvg.
When a logical volume with distributed extents is mirrored, the resulting
layout is commonly referred to as EXTENT-BASED MIRRORED STRIPES.
Note that EXTENT-BASED MIRRORED STRIPES can be created without the
distributed
allocation policy by adding one extent at a time to the desired physical
volumes through lvextend(1M).
Examples
Assume /dev/vg01/lvol1 is 4gb and striped across c1t5d0 and c1t6d0 with
with mirrors on c0t3d0 and c0t6d0 respectively, each of these disks being 2gb
PVs.
Prior to beginning the file /etc/lvmpvg would look like this:
# more /etc/lvmpvg
VG /dev/vg01
PVG PVG0
/dev/dsk/c1t5d0
/dev/dsk/c1t6d0
PVG PVG1
/dev/dsk/c0t3d0
/dev/dsk/c0t6d0
Assume you want to increase the lvol by another 1gb. Conventional thought would
indicate that you should add another disk but actually you must add 4 more
disks to satisfy the requirements of striping and mirroring with distributed
allocation and PVG strict policies.
# vgextend /dev/vg01 /dev/dsk/c1t3d0 /dev/dsk/c1t4d0 /dev/dsk/c0t5d0 \
/dev/dsk/c0t4d0
After you added 4 disks using vgextend, i.e. c1t3d0l, c1t4d0, c0t5d0 and