HP-UX Reference (11i v1 05/09) - 1M System Administration Commands A-M (vol 3)

l
lvcreate(1M) lvcreate(1M)
-C contiguous Set the contiguous allocation policy. A contiguous logical volume has three charac-
teristics:
• Physical extents are allocated in ascending order,
• No gap is allowed between physical extents within a mirror copy,
• Physical extents of any mirror copy all reside on a single physical volume.
Use the strict (-s) and contiguous (
-C) options together to form various combined
allocation policies on a logical volume. For example,
-s y -C y defines a logical
volume such that each mirror copy is contiguous, yet mirror copies of a logical
extent cannot share the same physical volume.
contiguous can have one of the following values:
y Set a contiguous allocation policy.
n Do not set a contiguous allocation policy. This is the default.
-d schedule Set the scheduling policy when a logical extent with more than one mirror is writ-
ten. (The scheduling policy of a striped logical volume is striped and cannot be
changed.) schedule can have one of the following values:
p Establish a parallel scheduling policy. This is the default.
s Establish a sequential scheduling policy. Use this value with care, because it
leads to performance loss in most cases.
-D distributed Set the distributed allocation policy. distributed can have one of the following
values:
y Turn on distributed allocation.
n Turn off distributed allocation. This is the default.
When the distributed allocation policy is turned on, only one free extent is allo-
cated from the first available physical volume. The next free extent is allocated
from the next available physical volume. Allocation of free extents proceeds in
round-robin order on the list of available physical volumes.
When the distributed allocation policy is turned off, all available free extents are
allocated from each available physical volume before proceeding to the next avail-
able physical volume. This is the default.
The distributed allocation policy REQUIRES the PVG-strict allocation policy ( -s
g
) to ensure that mirrors of distributed extents do not overlap (for maximum avai-
lability).
lvcreate(1M) will obtain the list of available physical volumes from
/etc/lvmpvg . See vgextend(1M) for more information on physical volume
groups and /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 dis-
tributed allocation policy by adding one extent at a time to the desired physical
volumes through lvextend(1M).
The distributed allocation policy is incompatible with the striped scheduling policy (
-i stripes ) and the contiguous allocation policy ( -C y ).
The lvchange(1M) command can be used to assign the distributed allocation policy
to an existing logical volume.
See lvdisplay(1M) for display values.
See EXAMPLES.
-i stripes Set the number of disks to stripe across. stripes must be in the range 2 to the
number of disks in the current volume group. -i and -I must be specified
together.
-I stripe_size Set the size in kilobytes of the stripe. stripe_size should be a power of 2 in the
range 4 to 32768. -i and -I must be specified together.
HP-UX 11i Version 1: September 2005 − 2 − Hewlett-Packard Company Section 1M−−445