HP-UX 11i v3 LVM New Features in HP-UX 11i v3 (September 2009)

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irror to) an existing
ing can be directed to
are based RAID
g the striping and mirroring processing, which allows LVM to provide the best of both
RAID 10 and RAID 01.
size and stripe width
you to create a
irrored logical volume as long as there are enough free extents in the volume group. The logical
volu layout then uses a slight variation of RAID 10 and all the benefits of RAID 10 are retained. For example,
Figure 2 shows a volume group with seven physical volumes and a logical volume striped across three disks with
one mirror copy.
RAID 10, only six
al volumes, PV0 does
ation. PV0 was short
two extents were allocated from PV1. LVM created the logical volume using seven physical
volumes resulting in a slight variation of RAID 10.
You can extend your existing striped logical volumes to a striped and mirrored configuration easily, using the
command to add mirrors. You cannot convert existing mirrored logical volumes to a striped and mirrored
configuration as explained in
ing and merging of striped and mirrored logical volumes. These logical volumes are also
s d in exclusive mode activation.
E
d across two physical volumes with one mirror copy and stripe
# lvcreate -L 90 -i 2 -I 64 -m 1 /dev/vgtest
Note: Striping with mirroring always uses strict allocation policies where copies of data do not exist on
the same physical disk. This results in a configuration similar to the RAID 01 as illustrated in Figure1.
• To create a logical volume of size 90MB striped across two physical volumes with one mirror copy and stripe
size of 64 KB and to create the mirror copies on specific disks ( configuration equivalent to RAID 01 as
illustrated in Figure1, enter)
# lvcreate -L 90 -i 2 -I 64 /dev/vgtest
# lvextend -m 1 /dev/vgtest/lvol1 /dev/dsk/c3t0d0 /dev/dsk/c3t1d0
You can create a new striped and mirrored logical volume from scratch, or extend (add m
striped logical volume. With the use of physical volume groups (PVGs), mirroring and strip
specific physical volumes. Without the constraint created by the nesting of levels in hardw
solutions, LVM is combinin
To create a pure RAID 10, ensure that the physical volumes have enough extents in terms of
to accommodate the logical volume. Otherwise, LVM optimizes the extent allocation to enable
striped and m
me
Figure 2: Example of LVM’s implementation of RAID 10 variation.
F
irst mirror
PV0 PV2 PV3
PV0 PV2 PV3
Secon
d
PV1 PV2 PV3
PV1 PV2 PV3
mirror
PV4 PV5 PV6
PV4 PV5 PV6
PV4 PV5 PV6
PV6
Stripes from PV
PV4 PV5
If the first physical volume used in the creation has enough extents (size of LV/3) to create
physical volumes are used, resulting in a strict RAID 1 0 configuration. But if one of the physic
not have enough free extents; LVM uses another physical volume, PV1, to complete the oper
by two extents so
lvextend
configuration. You can create any new logical volumes with striped and mirrored
the ‘Examples’ section.
LVM allows the splitt
upported in a clustered environment with shared an
xamples
Use any of the following procedures to create a striped and mirrored logical volume:
• To create a logical volume of size 90MB stripe
size of 64 KB, enter.