HP-UX Reference (11i v2 03/08) - 1M System Administration Commands A-M (vol 3)

l
lvcreate(1M) lvcreate(1M)
• 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,
-sy-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 mir-
ror is written. (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 fol-
lowing 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 allocated 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 physi-
cal 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 available 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 over-
lap (for maximum availability).
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 distributed 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 alloca-
tion 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.
Section 1M−−390 Hewlett-Packard Company − 2 − HP-UX 11i Version 2: August 2003