AIX Storage Management

•

Allocate each logical partition copy on a SEPARATE physical volume?

You can also ignore the

intra-disk

smit option:

•

POSITION on physical volume.

When you use smit, these fields have default values which can be ignored

because the map file physical partition allocation will have the higher

precedence.

For example, the use of the two map files badmir.map and badmir.map2 to

create the two copies of the perflv1 logical volume later will result in both copies

being placed on hdisk5. Hence, this gives you the same result as you would

obtain if you set

RANGE of physical volumes to minimum. This is why this field must

be ignored. If you try to change this field, you′ll get an error like

 

0516-690 mklv: The -a, -e, -u, -s, and -c options cannot be

used with the -m option.

Usage: mklv [-a IntraPolicy] [-b BadBlocks] [-c Copies] [-d Schedule]

[-e InterPolicy] [-i] [-L Label] [-m MapFile] [-r Relocate]

[-s Strict] [-t Type] [ -u UpperBound] [-v Verify&rbr. [-w MWC]

[-x MaxLPs] [-y LVname] [-Y Prefix] [-S StripeSize] VGname NumberOfLPs

[PVname...]

Makes a logical volume.

 

8.3.3 A Design Example for Improved Availability

This section will show you how to implement a mirrored environment that will

help you minimize the disruption caused by a hardware failure. The example in

this section assumes that you accept the cost of the extra disk capacity required

to implement mirroring.

If you do not have enough physical volumes to do this, then you can still improve

your availability by specifying minimum as the target range of physical volumes

during the creation of your logical volumes. This may be helpful if you know two

physical volumes in a volume group are much more reliable than another,

because if the less reliable physical volume fails, you may be able to access the

logical volumes that exist on one of the good disks.

We have already discussed a mirrored rootvg volume group, so this example

shows you how a non-rootvg volume group can be mirrored to provide higher

availability than in a non-mirrored environment.

Since mirroring requires a minimum of two physical volumes we will also show

how to identify these resources. We will use the name, availvg for our volume

group and and for our logical volume and journaled file system we expect to use

the names, availlv and availjfs respectively.

8.3.3.1 Command Line Summary

1. First check to see what disks are available and that they are not assigned to

an existing volume group:

 

# lspv

hdisk4 0000020158496d72 none

hdisk6 000002007bb618f5 none

#lsdev -Cc disk

hdisk4 Available 00-07-00-0,0 1.2 GB SCSI Disk Drive (in 2.4 GB Disk Unit)

hdisk6 Available 00-07-00-2,0 1.2 GB SCSI Disk Drive (in 2.4 GB Disk Unit)

 

208 AIX Storage Management

2. Create original non-rootvg using both physical volumes:

 

# mkvg -f -y′ availvg′ ′hdisk4 hdisk6′

 

3. Add a logical volume to the the volume group availvg creating two copies,

each on a different physical volume. The logical volume will consist of six

logical partitions:

 

# mklv -y′ availlv′ -e′ x′ -c′2′ -v′ y′ ′availvg′ ′6′

 

4. Create a journaled file system, /availjfs, using the logical volume created

above:

 

# crfs -v jfs -d′ availlv′ -m′/availjfs′ -A′ yes′ -p′ rw′ -t′ no′ \

-a frag=′4096′ -a nbpi=′4096′ -a compress=′ no′

 

5. Mount the journaled file system:

 

# mount /availjfs

 

6. Create a copy of the journaled log logical volume:

 

mklvcopy -e′ x′ ′-k′ ′loglv00′ ′2′

 

7. Turn off quorum checking:

 

# chvg -a′ y′ -Q′ n′ ′availvg′

 

You now have a volume group with mirrored logical volumes and a file system

mounted and ready to be used.

8.3.3.2 Detailed Description

The above summary steps have shown us how to create a mirrored volume

group. In this section we will look at each command separately, showing its

output and also verify that we have successfully created a mirrored volume

group.

How to Create a Mirrored non-rootvg Volume Group:

In order to create a

mirrored volume group we need two or more free physical volumes. In our

example we have chosen

hdisk4

and

hdisk6

, each capable of being powered on

and off separately. This will be useful in simulating a physical volume failure by

switching off one of the active physical volumes. A mirrored logical volume,

availlv, will be created with a size of six logical partitions (24MB), with each copy

on a separate physical volume.

In order to achieve high availability we need to make sure that for each of the

physical volumes selected for the volume group:

•

They are on different SCSI adapters.

•

They have their own power supply.

1. First let us look at the availability of the physical volumes for the volume

group. Execute the

lspv command to check which physical volumes are

currently not assigned to a volume group:

Chapter 8. Practical Examples 209