mklv

mklv Command (AIX)



Purpose

Creates a logical volume.

Syntax

mklv [ -a Position ] [ -b BadBlocks ] [ -c Copies ] [ -d Schedule
] [ -e Range ] [ -i ] [ -L Label ] [ -m MapFile ] [ -r Relocate
] [ -s Strict ] [ -t Type ] [ -u UpperBound ] [ -v Verify
] [ -w MirrorWriteConsistency ] [ -x Maximum ] [ -y NewLogicalVolume
| -Y Prefix ] [ -S StripeSize ] VolumeGroup Number [ PhysicalVolume
... ]

Description

Attention: This command is not allowed if the volume group is varied
on in concurrent mode.

The mklv command creates a new logical volume within the VolumeGroup.
For example, all file systems must be on separate logical volumes.
The mklv command allocates the number of logical partitions to the
new logical volume. If you specify one or more physical volumes with
the PhysicalVolume parameter, only those physical volumes are available
for allocating physical partitions; otherwise, all the physical volumes
within the volume group are available.

The default settings provide the most commonly used characteristics,
but use flags to tailor the logical volume to the requirements of
your system. Once a logical volume is created, its characteristics
can be changed with the chlv command.

The default allocation policy is to use a minimum number of physical
volumes per logical volume copy, to place the physical partitions
belonging to a copy as contiguously as possible, and then to place
the physical partitions in the desired region specified by the -a
flag. Also, by default, each copy of a logical partition is placed
on a separate physical volume.

The -m flag specifies exact physical partitions to be used when creating
the logical volume.

Physical partitions are numbered starting at the outermost edge with
number one.

Notes: 

1.	Changes made to the logical volume are not reflected in the file
systems. To change file system characteristics use the chfs command.

2.	Each logical volume has a control block. This logical volume control
block is the first few hundred bytes within the logical volume. Care
has to be taken when reading and writing directly to the logical volume
to allow for the control block. Logical volume data begins on the
second 512-byte block.

3.	A mirrored, or copied, logical volume is not supported as the active
dump device. System dump error messages will not be displayed, and
any subsequent dumps to a mirrored logical volume will fail.

4.	To use this command,  either have root user authority or
be a member of the system group.

5.	When creating a striped logical volume using the -S flag, 
specify two or more physical volumes or use the -u flag.

6.	When creating a striped logical volume, the number of partitions
must be an even multiple of the striping width.

You can use the System Management Interface Tool (SMIT) to run this
command. To use SMIT, enter:

smit mklv

Flags

Note:	The -c, -d, -e, -m, -s, and -w flags are not valid when creating
a striped logical volume using the -S flag.

-a Position	Sets the intra-physical volume allocation policy (the
position of the logical partitions on the physical volume). The Position
variable can be one of the following:

m	Allocates logical partitions in the outer middle section of each
physical volume. This is the default position.

c	Allocates logical partitions in the center section of each physical
volume.

e	Allocates logical partitions in the outer edge section of each physical
volume.

ie	Allocates logical partitions in the inner edge section of each
physical volume.

im	Allocates logical partitions in the inner middle section of each
physical volume.

-b BadBlocks	Sets the bad-block relocation policy. The Relocation
variable can be one of the following:

y	Causes bad-block relocation to occur. This is the default.

n	Prevents bad-block relocation from occurring.

-c Copies	Sets the number of physical partitions allocated for each
logical partition. The Copies variable can be set to a value from
1 to 3; the default is 1.

-d Schedule	Sets the scheduling policy when more than one logical
partition is written. The Schedule variable can be one of the following:

p	Establishes a parallel scheduling policy. This is the default for
scheduling policy.

s	Establishes a sequential scheduling policy.

-e Range	Sets the inter-physical volume allocation policy (the number
of physical volumes to extend across, using the volumes that provide
the best allocation). The Range value is limited by the UpperBound
variable, (set with the -u flag) and can be one of the following:

x	Allocates across the maximum number of physical volumes.

m	Allocates logical partitions across the minimum number of physical
volumes. This is the default range.

-i	Reads the PhysicalVolume parameter from standard input. Use the
-i flag only when PhysicalVolume is entered through standard input.

-L	Sets the logical volume label. The default label is None. The maximum
size of the label file is 127 characters.

Note:	If the logical volume is going to be used as a journaled file
system (JFS), then the JFS will use this field to store the mount
point of the file system on that logical volume for future reference.

-m MapFile	Specifies the exact physical partitions to allocate. Partitions
are used in the order given in the MapFile parameter. Used partitions
in the MapFile parameter are not legal, since the new logical volume
cannot occupy the same physical space as a previously allocated logical
volume. All physical partitions belonging to a copy are allocated
before allocating for the next copy of the logical volume. The MapFile
parameter format is: PVname:PPnum1[-PPnum2]. In this example, PVname
is a physical volume name (for example, hdisk0) as specified by the
system. It is one record per physical partition or a range of consecutive
physical partitions. PPnum is the physical partition number, which
can range from 1 to 1016.

PVname	Name of the physical volume as specified by the system.

PPnum	Physical partition number. Physical partition numbers can range
from 1 to 1016.

-r Relocate	Sets the reorganization relocation flag. For striped logical
volumes, the Relocate parameter must be set to n (the default for
striped logical volumes). The Relocate parameter can be one of the
following:

y	Allows the logical volume to be relocated during reorganization.
This is the default for relocation

n	Prevents the logical volume from being relocated during reorganization.

-s Strict	Determines the strict allocation policy. Copies of a logical
partition can be allocated to share or not to share the same physical
volume. The Strict parameter is represented by one of the following:

y	Sets a strict allocation policy, so copies for a logical partition
cannot share the same physical volume. This is the default for allocation
policy.

n	Does not set a strict allocation policy, so copies for a logical
partition can share the same physical volume.

-S StripeSize	Specifies the number of bytes per striped. Must be a
power of two, between 4K and 128K , for example 4K, 8K, 16K, 32K,
64K, or 128K.

-t Type	Sets the logical volume type. The standard types are jfs (file
systems), jfslog (journal file system logs), and paging (paging spaces),
but a user can define other logical volume types with this flag. You
cannot create a striped logical volume of type boot. The default is
jfs. If a log is manually created for a filesystem, the user must
run the logform command to clean out the new jfslog before the log
can be used. For example, to format the logical volume logdev, enter:

logform /dev/logdev

where /dev/logdev is the absolute path to the logical volume.

-u UpperBound 	Sets the maximum number of physical volumes for new
allocation. The value must be between one and the total number of
physical volumes. The default is the total number of physical volumes
in the volume group. When used to create a striped logical volume,
using the -S flag, the -u flag sets the number of physical volumes
being striped across.

-v Verify	Sets the write-verify state for the logical volume. Causes
(y) all writes to the logical volume to either be verified with a
follow-up read, or prevents (n) the verification of all writes to
the logical volume. The Verify parameter is represented by one of
the following:

n	Prevents the verification of all write operations to the logical
volume. This is the default for the -v flag.

y	Causes the verification of all write operations to the logical volume.

-w MirrorWriteConsistency	

y	Turns on mirror write consistency which insures data consistency
among mirrored copies of a logical volume during normal I/O processing.

n	No mirror write consistency. See the -f flag of the syncvg command.

-x Maximum	Sets the maximum number of logical partitions that can
be allocated to the logical volume. The default value is 512. The
number represented by the Number parameter must be equal to or less
than the number represented by the Maximum variable. The maximum number
of logical partitions per logical volume is 32,512.

-y NewLogicalVolume	Specifies the logical volume name to use instead
of using a system-generated name. Logical volume names must be unique
systemwide name, and can range from 1 to 15 characters. The name cannot
begin with a prefix already defined in the PdDv class in the Device
Configuration Database for other devices.

-Y Prefix	Specifies the Prefix to use instead of the prefix in a system-generated
name for the new logical volume. The prefix must be less than or equal
to 13 characters. A name cannot begin with a prefix already defined
in the PdDv class in the Device Configuration Database for other devices,
nor be a name already used by another device.

Examples

1.	To make a logical volume in volume group vg02 with one logical
partition and a total of two copies of the data, enter:

mklv -c 2 vg02 1

2.	To make a logical volume in volume group vg03 with nine logical
partitions and a total of three copies spread across a maximum of
two physical volumes, and whose allocation policy is not strict, enter:

mklv -c 3 -u 2 -s n vg03 9

3.	To make a logical volume in vg04 with five logical partitions allocated
across the center sections of the physical volumes when possible,
with no bad-block relocation, and whose type is paging, enter:

mklv -a c -t paging -b n vg04 5

4.	To make a logical volume in vg03 with 15 logical partitions chosen
from physical volumes hdisk5, hdisk6, and hdisk9, enter:

mklv vg03 15 hdisk5 hdisk6 hdisk9

5.	To make a striped logical volume in vg05 with a stripe size of
64K across 3 physical volumes and 12 logical partitions, enter:

mklv -u 3 -S 64K vg05 12

6.	To make a striped logical volume in vg05 with a stripe size of
8K across hdisk1, hdisk2, and hdisk3 and 12 logical partitions, enter:

mklv -S 8K vg05 12 hdisk1 hdisk2 hdisk3

Files

/usr/sbin	Directory where the mklv command resides.

/tmp	Directory where the temporary files are stored while the command
is running.

/dev	Directory where the character and block device entries for the
logical volume are created.

Related Information

The chfs command, chlv command, chpv command, extendlv command, mklvcopy
command, rmlvcopy command, syncvg command.

The Logical Volume Storage Overview in AIX Version 4 System Management
Guide: Operating System and Devices.

The System Management Interface Tool (SMIT) Overview in AIX Version
4 System Management Guide: Operating System and Devices.

AIX HACMP/6000 Concepts and Facilities.