UNIX: AIX LVM Best Practice

Here are the general rules of thumb when creating a new FS on AIX

1. Understand the requirement

• What is the FS size requested?
• Do we have free space in the VG?
• Does the LV need to be striped and the number of disks to be striped are?
• What is the LV policy of the VG?

2. What kind of FS need to have CIO?

Normally in most of the user defined FS, except AIX default system FS

3. What FS needs to be configured as striping?

A tough question, but most of the user defined FS require to striped except AIX's default system FS

Where striping is needed, the recommendation of LV configuration is usually "poor man" striping instead of "strict" striping (a lot of old AIX servers still use "strict" striping but the trend has move to "poor man"striping)

4. Why this "poor man" striping policy over "strict" striping policy?

Simply because it provides more flexibility in managing the FS when it comes to LV extension as compared with the latter

And the second most important reason is it makes a Unix system admin's life a hell lot easier to live!

5. A "poor man" striping has the following characteristics

If you look at the PP distribution you will know if it is striped or not

In comparison, a strict striping has the following key characteristics

6. An example on how to configure poor man striping LV with CIO on a production server

6.1 First we detect the LUN

# cfgmgr and # lspv -L commands

6.2 We then change the PV attribute

# chdev -l hdiskX -a 'hcheck_interval=0 rw_timeout=60'

6.3 Then we add the disks to the VG

# extendvg vkandi hdiskX hdiskX hdiskX hdiskX

6.4 Create poor man striping (stripe to 4 disks)

# mklv-e x -t jfs2 -b n -y lvkandi vgkandi 1000 hdiskX hdiskX hdiskX hdiskX

This will create an LV lvkandi in VG vgkandi with 1000 Logical Partitions

6.5 We then create a JFS on the LV defined

# crfs -v jfs2 -d lvkandi -m /hedkandi -A yes -p rw -a agblksize=4096

6.6 Enable CIO option

#chfs -a options=cio,rw /hedkandi

6.7 Mount the FS

# mkdir /hedkandi

# mount /hedkandi

# df -h /hedkandi

6.8 Verify that the LV is mounted as CIO

# mount | grep lvkandi

7. To check if a FS is configured as CIO

8. To check if a FS is mounted as CIO

9. To enable CIO on a FS

10. To change an existing LV policy from strict to poor man striping or vice versa

There isn't a direct solution that I know of, and my suggestion is that you do a backup and recreate the LV with the desired striping

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Now that we are done with LV, we go to VG creation guideline

It is recommended to configure a Vg as a Scalable VG with an exception for rootvg

A scalable VG will support up to 1024 Physical Volume

1. Creating a scalable VG

First we identiy the PV to use for the VG creation

Create scalable VG with the following commands

# smitty mkvg---------->Add a Scalable Volume Group

Fill in the "Volume Group Name" "Physical Volume Names" and leave the rest as default

2. How to determine a VG type

Adapted from notes from my former workplace